Bulletin No. 207 Series E, Chemistry and Physics, 36 

DEPARTMENT OF TEiE INTERIOR

UNITED STATES GEOLOGICAL SURVEY

CHARLES D. WALCOTT, DIRECTOR

THE

ACTION OF AMMONIUM CHLORIDE 

UPON SILICATES

BY

AND 

GKKOKG-IE Srj::ir,

WASHINGTON

GOVERNMEN.T PllINTING OFFICE

1902

CONTENTS.

Page.

Introductory statement......--..-..---.--.------.--.-..--.-.-----------. 7

Analcite-.....-.-.-.--.-.....-.--.'--------....--.-.--..._.-.---.-...---.--. 8

Leucite .....................'.................-....................^-..... 16

The constitution of analcite and leucite.........-..--.-..--...--.---------. 17

Pollucite---. ............................................................ 21

Natrolite--------------------------..-..-----------------.------ --------- 22

Scolecite ................,.:............-.....-.................--.--.... 24

Prehnite .....--.-............--.------------------------------ --------- 25

The trisilicic acids-.--.-.--..---..........-._-----...-.........-...----.- 26

Stilbite.............-..................-....-.-.-----...--.---.......... 29

Henlandite .......... .......................---.-..-.-..-...-----.--..--.. 81

Chabazite............................................................... 32

Thoinsonite...-.-.-..-...._.................---...-.-.-.----..-----..--.. 34

Lanmontite -.-.------.-..-------------.-..-.-..-.-------.-.-----........ 35

Pectolite ......:......... ......................................'.......;.., 36

Wollastonite ....'............................ ................:........... 39

Apophyllite. _.--._..._-....__.....:......___-------------....----..-...._ 39

Datolite................................................. ................ 40

Elaeolite........................................... ...................... 40

Cancrinite ----.---.--...--....--.......................................... 41

Sodalite _......;................'......................................... 42

The feldspars...........-........--...............................'........ 43

Olivine ....1.......-------....--..--...-.-...---..----......--........... 44

Ilvaite..'..........................................._...................... 44

Riebeckite (?)...--.-..-.-.....-..............................^............. 45

JEgirite ......................................... .1...................... 46

Calamine.._....................--..-.--.....--.--..--......--. ---------- 47

Pyrophyllite..........-......--.-.......:..........................._....... 49

Serpentine....--.--.-..--.-.-...---.-..--................................. 51

Phlogopite ---..--.----.-----.--------............ ........-........-.... 51

Leuchtenbergite.................. ---..-....---.-................._..... 52

Xanthophyllite .--..-...-..-....-..-..:.......-.-........................ 53

The action of ammonium chloride on rocks.-.-----....-.-................. 53

Summary................................................................ 57

3

LETTER OF TRANSMITTAL.

DEPARTMENT OF THE INTERIOR,

UNITED STATES GEOLOGICAL SURVEY,

Washington, D. C., September 26, 

SIR: I have the honor to transmit herewith a memoir by Messrs. 

Clarke and Steiger on the action of ammonium chloride upon silicates, 

with the recommendation that it be published as a bulletin. These 

researches are of great geological importance for the light they throw 

upon the rational constitution of minerals. They are based on a 

method which is wholly novel and which is capable of wide application. The work is most creditable to the authors and to the United 

States Geological Survey.

Very respectfully, your obedient servant,

GEORGE F. BECKER,

Geologist in Charge, 

Division of Chemical and Physical Research.

Hon. CHARLES D. WALCOTT,

Director United States Geological Survey.

THE ACTION OF AMMONIUM CHLORIDE UPON

SILICATES.

By FRANK WIGGLESWORTH CLARKE and GEORGE STEIGER.

INTRODUCTORY STATEMENT.

In a series of investigations by Clarke and Schneider, which weiv 

carried out in the laboratory of the United States Geological Survey 

between the years 1889 and 1892, a a number of reactions were studied 

which shed some light upon the constitution of the natural silicates. 

Among these reactions two were of peculiar interest, on account of 

their simplicity and the ease with which they could be applied.

First, in the case of talc, it was found that one-fourth of the silica 

could be liberated by ignition; and that the fraction thus set free 

was measurable by solution in aqueous sodium carbonate. This 

reaction suggests that other acid metasilicates may behave in a similar way, and that we perhaps have a means of discrimination between, 

such salts and other compounds which simulate them. In other 

words, an acid metasilicate may be experimentally distinguished 

from a pseudo-metasilicate by the way in which it splits up when 

ignited. Evidence bearing upon this supposition will be found in 

the present paper.

The second of the reactions just referred to is that between dry 

ammonium chloride, at its temperature of dissociation, and various 

silicates, different minerals being very differently attacked. Some 

are completely decomposed, others are affected but slightly, and in 

certain cases substitutions are produced of a most suggestive character. To a certain extent, the two reactions overlap; that is, each 

one bears somewhat upon the other, and hence both have received 

consideration in the present series of researches.

In the earlier stages of our work the several silicates which were 

studied were heated with dry ammonium chloride in open platinum 

crucibles. The temperature chosen was 350°, at which point the 

chloride breaks up into gaseous Irydrochloric acid and free ammonia,

"Bulls. U. S. Geol. Survey No. 78, p. 11; No. 90, p. 11; No. 113, pp. 27, 34.
8 ACTION OF AMMONIUM CHLORIDE ON SILICATES. [BULL. 207,

and in this way partial changes were effected. Later, the heatings 

were performed in sealed combustion tubes, and then the reaction 

proved to be much more far-reaching. In nearly every case the 

material taken for investigation was 'ground up into one large, uniform sample, upon which all the experiments Avere performed, and 

in that way the results obtained are comparable with one another. 

The few exceptions to this rule of procedure will be noticed at the 

proper places. In. testing for soluble silica, a" standard solution of 

sodium carbonate, containing 250 grams to the. liter, was used, and 

here again the experimental conditions have been kept uniform. So 

much premised, we may proceed to the description of our iiwestigations, species by species, in detail.

ANALCITE.

Analcite, from many points of view, is a species of peculiar interest, and of late years it has received a great deal of attention. Its 

formula may be written in various ways, especially as regards the 

interpretation of its one molecule of water; but evidence too often 

has yielded before preconceived opinion. Additional evidence is now 

available, partly from the experiments of Friedel, and partly from 

the data obtained during the present investigation.

The analcite first examined by us was in well-developed crystals 

from Wassons Bluff in Nova Scotia. A uniform sample was prepared, as usual, and the analysis, given below, is contrasted with the 

theoretical composition required by the accepted empirical formula 

NaAlS:i2Oc . H2O.

Si02 . .................

ALA ..............................................'..

FeA ....... ..-i__. _____.___________._____;_________:

CaO .....'............................................

Na2O ---..___.._.. __________.__________ . . ..

H20at 100° ................._......._.................

H2Oover 100° 

Pound.

57.06

21 .-48

.13

 .16

12.20

.58

8.38

99. 99

Calctilated.

KA KK

23.18

14. 09

8.18

100. 00

Fractions of water.

At 100° -_--.---._...._,_.._ _._.____._.....______..____._____ 0.58

At 180°.........---.........................-...'-............ 1.16

At 260°.-.-......."..........-.........-..............-..-.-. 3.64

At 300°.......-.................:........................... 1.57

Low redness................................................. 1.90

Full redness ...............................'................. .11

Blast .-_--.-._.--..____........ ....................._....... none
C1.ARKE AND! ATVTATPTTTT Q STE1GER. J AJNALiOllJb. V

The fractional water determinations were made by heating in an 

air bath to constant weight at each temperature up to 300°, and 

finally over the direct flame. The first fraction, at 100°, is evidently 

hygroscopic or extraneous water, which can be disregarded. The 

remainder of the water, 8.38 per cent, belongs to the species. The 

significance of the analytical figures will be considered later.

Upon boiling the powdered anal cite with the standard sodium carbonate solution, 0.73 per cent of silica was extracted. After ignition 

the mineral in two determinations yielded 1.46 and 1.38 per cent, 

respectively. ,The splitting off of silica is, therefore, very slight; and 

one of the formulas proposed by Doelter," Na2 AlaSi2 08 +2H2Si03 , may 

be set aside as improbable. Metasilicic acid, or an acid metasilicate, 

can hardly be present in analcite; although the possibility of a neutral 

metasilicate,' as indicated by the empirical formula, is not excluded. 

If Doelter's formula were correct, one-half of the silica should be 

liberated by ignition.

Upon heating analcite with dry ammonium chloride, notable results 

were obtained even in an open platinum crucible. Sodium chloride 

was formed, which could be leached out by water and measured, 

while ammonia, free from chlorine, was retained by the residue to a 

notable and surprisingly stable degree. The experiments in detail 

were as follows:

A. Analcite, mixed with four times its weight of ammonium chloride, was 

heated for four hours to 350°. There was a gain in weight of 2.18 per cent, and 

6.10 per cent of soda, or one-half of the total amount, was converted into^NaCl, 

which was leached out by water, examined as to its purity, and weighed. In the 

residue 1.20 per cent of silica was extracted by sodium carbonate, showing that 

no more splitting off had occurred than was previously observed. The gain in 

weight, as will be seen from subsequent experiments, is due to the -fact that all of 

the NH4C1 had not been driven off, or else that more water was retained.

B. Analcite was ground up with four times its weight of NH4C1, heated for 

several hours, reground with another fourfold portion of chloride, and heated to 

350° for twenty-one hours. Gain in weight, 0.08 per cent. 5.57 per cent of soda 

was extracted as chloride.

C. Analcite heated to 350° for eight hours with four, times its weight of NH4C1. 

Loss, of weight, 0.10 per cent.

D. Six grams of mineral and 28 of chloride, mixed by thorough grinding, were 

heated to 350° for fourteen hours; then were reground with 28 grams of fresh 

NH4C1 and heated for thirty-five hours. Loss of weight, 0.13 per cent. 5.07 per 

cent of soda was extracted as chloride, plus 0.14 of ammonium chloride unexpelietl. 

2.03 per cent of silica was rendered soluble in sodium carbonate.

So far three facts are noticeable. First, the weight of the mineral 

after treatment is almost exactly the same as before, showing that 

gains and losses have balanced each other. Secondly, little silica has 

been split off. Thirdly, approximately, but not rigorously, one-half 

of the soda has been converted into NaCl. In A it was exactly half; 

in the other experiments, a little less than half. Furthermore, in the 

sodium chloride dissolved out, there is only a very little ammonium

aNeues Jahrbuch, 1890, Vol. I, p. 133.
10 ACTION OF AMMONIUM CHLOKIDE ON SILICATES. [BULL. 207.

chloride, amounting at most to 0.14 per cent, calculated upon the 

weight of the original mineral.

In the residue of the analcite after. extraction of sodium chloride, 

abundant ammonia can be detected, with either no chlorine or at 

most a doubtful trace. If, however, the unleached mineral, still 

retaining its sodium chloride, be heated strongly, say, from 400° up 

to redness, "NH4C1 is regenerated and given off. Its absence, as such, 

both from the leach and the residue was repeatedly proved. The 

ammonia and water retained by the analcite after heating to 350° with 

ammonium chloride were several times determined, and the following 

percentages, still reckoned on the original mineral, were found:

In B- .-..--.....'-.-.-...._.-..-........___...__.__

InC............... ................... ...............

InD.. ................................................

a

u

Mean. ......................................'-......

NH 3 .

2.03

2.19

2.36

2.35

2.06

2.20

H 2 0.

2 25

2.00

1.89

2.04

Correcting the ammonia for the 0.14 of NH4C1 found in D, the mean 

value becomes 2.15. The determinations of it were made by three 

distinct methods, and there is no possible doubt as to its presence.

The composition of the analcite after the treatment with ammonium 

chloride may now be considered, with the subjoined combination of 

the data. The NaCl in A, 11.50 per cent, was in material which had 

gained 2.18 per cent, and is subject to a correction which reduces the 

figure to 11.26. In B, C, and D the corresponding correction is so 

small that it may be neglected. The last column gives the composition of the leached residue, recalculated to 100 per cent, after deduction of NaCl and the soluble silica. The letters refer back to the 

several experiments, and the little iron is included with the alumina.

Sol. SiOj.. ........ ...1......

Insol. SiCX,--------. .........

AT r>

CaO--.-_ .. .................

Naa... .................. ..

Na2O-. ......................

NH3 .......................

H.2O. .......................

A.

1.20

11.26

B.

10.50

2.03

2 25

C.

2.19

2.00

D;

2.03

54.96

21. 37

.16

9.57

7.12

2.21

1.89

99.31

Average.

1.61

54.96

21.37

.16

10.44

7 12

2.15

 . 2 04

99.85

Residue.

62.59

24.34

.18

8.11

2.46

2.32

100. 00
CLARKE AND")

STEIGEIl. J ANAICITE. 11

The results thus obtained with analcite from Nova Scotia were so 

remarkable that further investigation seemed to be needed upon 

material of different origin, and with variation in the details of 

manipulation. The new experiments, which have led to highly interesting consequences, are now to be described.

To the kindness of President Regis Chauvenet, of the State School 

of Mines, we are indebted for a liberal supply of well-crystallized 

analcite from North Table Mountain, near Golden, Colo., of which a 

uniform sample of about 80 grams Avas prepared. An analysis of 

the mineral gave the following results:

SiO,-. ,-. -.-I - -- --- 55.72

CaO- .17

12.46

E^O at 100°.. .----.- -I----------- --------- ------- ---------- 0.13

H,0 above 100° -.._..._.--............-----.------..--------- 8.26

Water by fractions.

99.80

At 100°...-.-.--.-----.-.----.-----..--,- .-----.....---.-.-_ 0.13

At ISO0 ..-.....-..-........--....--..-----.--.-.---.-.---.--- .75

At 260°-........-......-----.......----. -...-..--.... 2.44

At 300°. ...........-..- -. .---...------ ---------- 1.28

At 3500 -.....-.---.-....-...-----.---.. ---- --.-.--.-- 1.76

At redness.-..---------------------------.-------.----- 2.03

Above a low red heat no further loss of weight was observed. Upon 

boiling the powdered mineral for fifteen minutes Avith the standard 

solution of sodium carbonate, 0.45 per cent of silica Avas dissolved. 

After ignition, 0.57 per cent was soluble, which is practically the 

same amount. No silica Avas split off by heating. The experiments 

with ammonium chloride fall into two series. The first of these Avas 

conducted precisely as in the case of the Nova Scotian material, 

namely, by grinding the pOAvdered mineral into an intimate mixture 

with four times its Aveight of the chloride, and heating in an open 

crucible. In three cases the material, after volatilization of the 

ammonium chloride, Avas reground Avith a fresh amount of the salt, 

and then heated again. The temperature and duration of the experiments Avere purposely someAvhat varied. After heating, the material 

Avas leached out Avith Avater, the sodium chloride which had been formed 

Avas estimated, and in the residue the fixed ammonia was determined.

In this series there Avere four experiments, with results as folloAvs:

A .-...-.... ........-I........

B

C ..-.....--__....-__...- -..

D ... . ....... ..... ....

Hours 

heated.

28

8*

26

5

Ternperatiire.

300

350

350

340-380

Soda removed.

4.75

6.36

3.76

6.70

Ammonia 

in residue.

2.04

2.88

1.72

2.85
12 ACTION OF AMMONIUM CHLORIDE ON SILICATES. [BOLL. 207.

In the analcite from Nova Scotia the ammonia retained by the 

leached residue ranged from 2.03 to 2.36 per cent, while the extracted 

soda-varied from 5.07 to 6.10. In two of the new experiments these 

figures are perceptibly exceeded,. and the}7 represent the shortest 

duration of heating. Prolonged heating seems to be undesirable, and 

seems to undo a part of .the reaction which has taken place; otherwise 

the results obtained are of the same order as their predecessors. 

About one-half of the soda in the analcite is converted into chloride, 

while variable ammonia is retained.

In the second series of experiments a sealed tube was substituted 

for the open crucible. . The powdered analcite was intimately ground 

with four times its weight of ammonium chloride, as before, and then 

heated to 350° in a tube furnace for from four to eleven hours. Under 

these conditions practically the whole of the soda in the mineral was 

converted into sodium chloride, while all of the liberated ammonia 

was absorbed by the residual silicate. Upon leaching the contents 

of the tube with water, to remove sodium and ammonium chlorides, 

a residue was obtained which exhibited constant composition whether 

dried at 100° or at the ordinary temperature of the air. Three 

samples of the residue were prepared and analyzed; other samples 

were partially examined and used for subsidiary experiments. The 

three analyses, lettered for future reference, were as follows, the 

analcite itself being included in the table for comparison:

SiO, ........... .........'..-..........

Al O

CaO ............._...__.._ ..._.......

NajjO .............. .... ..

NH3 .................................

HaO-.. ..............................

Analcite.

55.72

23,06

.17

12 46

8.39

99. 80

Residue A.

61.93

25.21

. .40

7.23

4.50

99. 27

Residue B.

61i68

25.33

22

6.95

4.91

99.09

Residue C.

61.79

25.24

no

"7.71

K Al

100.03

Residue C was prepared with the greatest care, and was air dried. 

Exposed over sulphuric acid in a vacuum desiccator for fourteen days, 

it lost in weight only 0.08 per cent. Tested for chlorine, only a slight 

trace could be recognized, but upon boiling for fifteen minutes'with 

sodium carbonate solution it yielded 1.97 of soluble silica. After 

ignition only 1.70 of silica was soluble, or somewhat less than before. 

Upon heating to constant weight at 300°, only 0.46 per cent was lost, 

but at 350° it slowly decomposed, giving off ammonia. At 300° the 

compound is stable.

The 0.28 per cent of soda remaining in residue C may be regarded 

as representing unaltered analcite, doubtless coarser particles which
CLAKKE AND"] 

STEJGEE. J ANALCITE. 13

escaped complete transformation. It corresponds to 1.98 per cent of 

analcite, which, together with the 1.97 of soluble silica and the 0.46 

of water lost below 300°, may be deducted from the substance in 

order to obtain the composition of the definite compound. The latter 

amounts to 94.72 per cent of the total residue, and agrees very nearly 

in composition with the formula

2NI-I3 .H2O.Al203 .4SiO2 . . .'1

Recalculating the 94.72 of residue to 100 per cent, we get the following comparison between analysis and theory:

sioa ------- - .--- -, .-.. 

A1A------ ----------------------------- ------------

NH, .................................................

H2O.-- ---------------------------------------------

Pound.

61.07

26. 15

8.14

4.64

100. 00

Calculated.

60. 92

'25.88

8.63

4. 57

100. 00

Written in rational form the compound becomes equivalent to an 

anhydrous ammonium analcite, .

NH4AlSi2Oc ;

that is, analcite in which sodium has been replaced by ammonium. 

From this point of view the reaction between analcite and ammonium 

chloride becomes a simple case of double decomposition, and is perfectly intelligible. To establish this conclusion, however, corroborative experiments were necessary.

In the first place, the observed equivalency between the sodium 

lost and the ammonia gained might be due to a mere coincidence, and 

so far be illusory. One atom of sodium, taking chlorine from ammonium chloride, liberates one molecule of ammonia, the amount which 

the analcite residue has retained. Suppose more ammonia were present; could it be absorbed'?

To answer this question another tube was prepared, with the usual 

mixture of analcite and ammonium chloride. This was covered by a 

loose plug of glass wool, in front of which we placed enough pure 

lime to liberate about double the normal amount of ammonia. The 

tube was then sealed, and heated to 350°, as in the previous experiments. Upon opening the tube, a strong outrush of ammonia was 

noticed; but in the leached and thoroughly washed residue, only 7.52 

per cent.of ammonia was found. This quantity agrees with that from, 

the previous samples, and shows that the limit of the reaction has 

been practically reached. One molecule of ammonia is retained, and 

no more.

Still another experiment was tried upon a portion of the residue 

marked C. If the compound is really an ammonium salt, it should
14 ACTION OF AMMONIUM CHLORIDE ON SILICATES. [BULL. 207.

be decomposable by caustic soda in such a way as to reverse the reaction by which it had been obtained. The substance, however, is very 

insoluble, so that the reaction takes place slowly. To phenol phthalein it is absolutely neutral, and with Nessler's reagent it reacts only 

after long standing.

To settle the question a weighed portion of the compound was boiled 

in a distilling flask with a 10 per cent solution of sodium hydroxide, 

to which wrater was added from time to time. The distillate was collected in a tube containing aqueous hydrochloric acid; and the 

ammonia which passed over was weighed, ultimately as chloroplatinate. By four hours' boiling 6.90 per cent of ammonium was driven 

off and determined; and the residue remaining in the flask, after 

washing until no alkaline reaction could be detected in the washwater, was examined for soda, of which 10.41 per cent was found. 

The anticipated reaction had taken place, although not completely; 

it was enough, however, to confirm our opinion, and to establish the 

nature of the new compound beyond reasonable doubt. Other confirmation was obtained later, from the study of leucite.

The foregoing paragraphs now enable us to understand a phenomenon which we observed in our work with the open crucible. In that 

case a partial reaction takes place between the analcite and the 

ammonium chloride, producing, as in the sealed tube, a mixture of 

an ammonium alumino-silicate with sodium chloride: the two substances being separable by leaching. But if, instead of leaching, the 

mixture be heated to full redness, ammonium chloride is re-formed 

and given off, leaving a residue which contains little or no sodium 

chloride, and is wholly insoluble, or almost so, in water. That is, 

the reaction which occurs at 350° is reversed at the higher temerature, 

and anhydrous analcite, or an isomer of it, is regenerated. Ammonium and sodium again change places, and the original state of molecular equilibrium is restored.

What, now, is the nature of the product obtained in the open crucible after sodium chloride has been removed? Is it a definite intermediate compound or an indeterminate mixture? At first we were 

inclined to accept the first of these alternatives, and we assigned to 

the substance the formula H2Na2Al4Si8O24 .NH3 , in which the ammonia 

plays a part equivalent to that of water. In this expression we were 

influenced by the researches of Friedel,a who had shown that ammonia 

could in part replace the "zeolitic" water of analcite; but it now 

appears that the phenomenon observed by him. is quite distinct from 

that discovered by us, and is, indeed, of an entirely different order. 

We may, therefore, in accordance with our new data, rearrange the 

formula, transforming it to that of an ammonium salt, HNa2NH4Al4 

Si8024 , the agreement with the analytical figures being approximate 

only. The resiilts obtained are not sharp enough for certainty.

This product we are now inclined to regard as a mixture, although

a Bull. Soc. min. France, Vol. XIX, p. 94,1896,
CLARKE AND"! 

STEIOEB. J ANALCITE. 15

it is not strictly intermediate between arialcite and its final ammonium 

derivative. Only half of the eliminated sodium has been replaced 

by ammonium, while hydrogen, or water, makes up the deficiency. 

It seems probable that the reaction in the sealed tube and that in the 

open crucible are at first essentially the same, but that in the latter 

case secondary reactions follow, which cause the variations in the 

final results. In the sealed tube the element of pressure comes into 

play, and the reaction is complete. In the open, crucible pressure is 

lacking; some ammonia escapes fixation and reacts upon a part of the 

sodium chloride which was at first formed; hence the composition of 

the leached residue is essentially modified. This residue may be a 

definite compound, but the case in its favor is unproved and the 

presumption is rather against it.

The most remarkable fact developed by the foregoing experiments 

is the easy replaceability of the soda in analcite. This replace/ability, 

however, is not limited to the substitution of ammonium for sodium; 

it appears to extend to other bases as well, and this we have proved 

in the case of silver. This is illustrated by three experiments upon 

the Colorado analcite, as follows:

A. Analcite, intimately mixed with dry silver nitrate, was heated in a sealed 

tube to 400° for four hours.

B. Analcite and silver nitrate were heated in a sealed tube to 250° for fotir hours.

C. Ammonium analcite, mixed with dry silver nitrate, was heated in a sealed 

tube to 250° for four hours.

All the products of these heatings were leached with water, and 

washed until the filtrates gave no test for silver; the residues were 

then dried on the water bath. The product in each case was a white 

powder not differing in appearance from the original material.

The analyses of the different portions are given below, together with 

the composition of the theoretical compound, AgAlSi2 06 .IT2O, which 

is given in column D.

Si02 .................................

AljO, -.-------.--------------------.

AgaO... ..............................

Na2O... ......... ..J..................

H,o. - .:- -,-

"TCTT

A.

41.31

- 16.44

37.45

.85

4.29

100. 34

B.

40.08

16.29

36. 91

.81

5.86

none

99.95

C.

42. 69

18. 22

32.01

.68

6.08

.69

none

 100.37

D.

39.35

16.72

38.03

5.90

100. 00

From preparation A, 13.13 per cent of the soda in the original mineral was found in the leach water; and in B, 12.57 per cent. These 

quantities are slightly in excess of the amount actually present in the 

analcite, for the reason that a little other material which passed into
16 ACTION -OF AMMONIUM CHLORIDE ON SILICATES. [BULL.-207.

the filtrates was not separated from the soda. It is enough to show 

that a true silver analcite has been formed, and that the transformation is practically complete. A similar reaction takes place between 

silver nitrate and chabazite, but the product as yet has not been 

exhaustively examined. The reaction, it will be observed, is analogous to that by which silver ultramarine is produced, and it suggests 

a promising line of experimentation for the future.

LEUCITE.

Between analcite and lencite the closest analogies have long been 

recognized. The two minerals have similar composition, they resemble 

each other in crystalline form, and they yield, upon alteration, products of the same order. Recently also, analcite, like leucite, has been 

identified as a not uncommon constituent of volcanic rocks; analcite 

basalt being a good example., In view of these resemblances it was 

plainly desirable to compare the minerals by means of the ammonium 

chloride reaction, a task which has been performed with satisfactory 

results.

In a preliminary experiment a sample of leucite taken without 

regard to purity was heated with ammonium chloride to 350° in a 

sealed tube. Potassium, chloride was formed corresponding to 18.06 

per cent of potash, and in the leached residue 6.90 per cent of 

ammonia was found. The foreseen reaction had occurred, and more 

careful work was accordingly undertaken.

Our material consisted of a large, irregular crystal of leucite from 

Vesuvius, which yielded about 20 grams of the pure mineral. This 

was ground to a uniform sample, and a portion of it was analyzed; 

the analysis will be given presently. The sealed-tube experiments 

were conducted precisely as in the case of analcite, and they confirmed 

both the preliminary test and our anticipations. Chlorides were 

formed equivalent to 18.53 per cent of potash, 1.08 of soda, and 0.08 

of alumina; the reaction, therefore, was very nearly complete. The 

leached residue was then analyzed, and the data, compared with the 

analysis of the original mineral, were as follows:

SiO2 .----- ------------- ...............................

Al O

CaO..--. ........-....................'................

K2O..---- ---------------------------------------- ----

Na2O. --------- -------------.-------------.----.------

NH3 .--_..___._.--___..__-.--._..____.-.._-

'H20. -------------------------------------------------

Leucite.

55.40

23.69

.16

19.54

1.25

 24

100. 28

Residue.

60.63

26.44

.50

.25

7.35

5.17

100.34
CLARKE AND"! 

STEIGEK. J

LEUCITE. 17

Leucite, then, gives the same reaction as analcite and yields the 

same ammonium compound. A closer agreement in the composition 

of the latter could not reasonably be demanded. Ammonium leucite 

is formed in both cases by ordinary double decomposition in a state 

of approximate purity; the first silicate of ammonium, we think, 

which has ever been prepared.

As a further check upon the results so far obtained, an attempt was 

made to transform ammonium leucite into the corresponding lime 

salt, CaAl2Si4 012 , by fusion with calcium chloride. The ammonium 

leucite was mixed with a saturated solution of calcium chloride, which 

was evaporated to dryness, then heated gradually to dehydration, and 

finally fused. Ammonium chloride was given off and identified. 

Upon treating the fused mass with water, filtering and thoroughly 

washing the residue, a white powder was obtained which, after drying 

at 100°, was analyzed. It was also examined microscopically by Mr. 

J. S. Diller, who found it to consist of apparently isotrppic grains, 

showing traces of incipient crystallization. The following analysis is 

contrasted with the theoretical composition of calcium leucite, from 

which it varies considerably.

SiO, .................................................

ALA ------------------------------------- -----'.

CaO ..................................................

K2 0, .................................................

Na,0 ..........................................'......

01 ............................................. .......

Found.

54.35

26.23

17.38

.16

.25

.28

1.24

99.89

Calculated.

60.80

25.63

14.07

100.00

Evidently the desired salt was not definitely obtained, and the 

product appears to be a mixture. The reaction, however, tends in 

the right direction, and deserves further study under other conditions. Probably the water which was present in the mixture of silicate and chloride took part in the changes produced, although of this 

we can not be certain. It is interesting to note that the product 

obtained approximates in composition to the meteoric mineral maskelynite, which is regarded by Groth as probably equivalent to a 

calcium leucite.

THE CONSTITUTION OF ANALCITE AND LEUCITE.

In all of the earlier attempts to discuss the constitution of analcite 

the molecule of water which it contains has been a chief element of 

uncertainty. Should it be regarded as representing hydroxyl or as

9506 No. 207 02 2
18 ACTION OF AMMONIUM CHLORIDE ON SILICATES. [BULL. 207.

water of crystallization? That question arose first of all. Under the 

first interpretation analcite became a diorthosilicate: Al]STaH2Si2O7 ; 

under the latter its equivalency with leucite appeared. The researches 

of Friedel, however, have settled this question in part, and whatever 

the function of the water may be it is something outside of the true 

chemical molecule; for all the water can be expelled from analcite 

by heat, without destruction of the crystalline nucleus, the anhydrous 

salt, and it is taken np again upon exposure of the dehydrated mineral to moist air. But whatever its mode of union may ultimately 

prove to be, the amount of water in analcite corresponds to the simple 

molecular ratio which is shown in the ordinary formula of the species. 

One molecule of analcite holds a certain definite number of water 

molecules, and Friedel's observations are not incompatible with the 

idea that these are retained with varying degrees of tenacity. This 

idea is suggested by the various series of fractionation experiments 

which have been made from time to time by independent workers, 

even though the data are not by any means concordant. Thus 

Lepierre a found that half the water of analcite was driven off at or 

below 300°, the other half above 440°. In our own experiments threefourths were expelled at 300°, the remaining fourth being held up to 

a much higher but undetermined temperature. In both series the 

water fractions are represented by fourths, but Friedel's experiments 6 indicate a continuity of loss in weight of a quite dissimilar 

order. Friedel holds that all of the water fractionations heretofore 

made upon analcite are fallacious, and that no definite fractions can 

be identified a conclusion strongly supported by his own data, even 

though the proof is not absolutely positive. The most that can be 

said is that the weight of evidence so far is in favor of Friedel's 

contention, but that additional investigation is necessary in order to 

reconcile all discrepancies. The full significance of the water in

analcite remains unknown.

Eliminating the water from analcite, the empirical formulae for 

both analcite and leucite appear at once to be identical in form and 

to represent salts of ordinary metasilicic acid. Indeed, both minerals 

have been commonly regarded as metasilicates; but upon this point 

the production of the ammonium derivatives now sheds a new light. 

In the formation of the latter compounds the fixed bases of the 

original salts have been replaced by a volatile base, and the substances 

so formed split up upon ignition in such a way as to give evidence 

regarding their constitution.

For example, if ammonium leucite is a true metasilicate, a salt of 

the acid H2Si03 , it should break up, when ignited, in accordance 

with the following equation:

2NH4Al(SiO3 ) 2 =Al2 (Si03 ) 3 +2NH3 +H2 0+Si02 ;

« Bull. Soc. chim. France, 3d series. Vol. XV, p. 561,1896. 

6 Bull. Soc. ruin. France, Vol. XIX, p. 363,1896.
CONSTITUTION OF ANALCITE AND LEUCITE. . 19

that is, one-fourth of the silica ought to be set free, measurable by 

extraction with, sodium carbonate solution. No such splitting off 

occurs, however. An ammonium leucite which already contained 1.97 

per cent of soluble silica gave only 1.70 per cent after ignition; hence 

no additional silica had been liberated. We may conclude, therefore, 

that analcite and leucite are not true metasilicates, but pseudo-compounds, either salts of a polymer of metasilicic acid or mixtures, of 

ortho- and trisilicates analogous to those which we find among the 

plagioclase feldspars and in the mica group.

In order to discuss the constitution of analcite, let us recur to our 

analysis of the variety from Nova Scotia. It is at once evident from 

the comparison made on a preceding page that our sample of the 

mineral varies notably in composition from the requirements of 

theory. The silica is 2£ per cent too high, while alumina and soda 

are correspondingly low. No probable impurity and no presumable 

errors of manipulation can account for so great a divergence. If we 

consult other analyses, as we find them tabulated in manuals like 

those of Dana and Hintze, we shall find other cases resembling this, 

and also examples of variation in the opposite direction, with silica 

low and an apparent excess of bases. Most analcite gives quite 

sharply the metasilicate ratios required by the accepted formula; 

but the variations from it are large enough, common enough, and 

regular enough to command attention. The analyses are not all 

covered by the recognized theory, and the apparent irregularities are 

not fortuitous, but are systematic in character.

One explanation of the seeming anomalies is simple and clear. If 

analcite, instead of being a metasilicate, is really a mixture of ortho 

and trisilicate, then all of the analyses become intelligible. In most 

cases the two salts are commingled in the normal ratio of 1:1, but in 

our analcite the trisilicate predominates, while in some other samples 

the ortho-salt is in excess. All reduce alike to the simple expression

NaAlX.H20,

in which X represents nSi04 +mSi3O8 , a formula which agrees with 

evidence from various other sources.

For example, analcite may be derived in nature either from albite, 

AINaSigOg, or nephelite, AlNaSiO4 , and on the other hand alterations 

of it into feldspars have been observed. Its closest analogue, leucite, 

has yielded pseudomorphs of orthoclase and elaeolite, while leucite 

and analcite are mutually convertible each into the other. The evidence of this character the evidence of relationship between analcite 

and other species is varied and abundant, and the simplest conclusion 

to be drawn from it is that which has been given. Every alteration, 

every derivation, every variation in the composition of analcite points 

to the same belief. The consistency of the data can not well be 

denied.
20 ACTION OF AMMONIUM CHLOEIDE ON SILICATES. [BULL. 207.

In the case of a normal analcite that is, one which conforms to the 

usual empirical formula the expression which best represents these 

relations is

Al4Na4 (Si04 ) 2 (Si3 08 ) 2 . 4H2 0;

and leucite is the corresponding potassium salt, but anhydrous. 

Structurally this is comparable with the formulae of garnet, zunyite, 

sodalite, and noselite, all of which are isometric in crystallization. 

The more important of the symbols are as follows:

^Si04 =Ca

/ . /Ca 

Al SiO4 = Ca. AlSi04 ==Al 

Garnet.

Si04 =Ka

Al Si3O8=K2

SiO4 =Na2

NAI-CI

-SiO4 =Na2 AlSiO4 =Na2

\ 

/

Al-SCX-NaSodalite.

SiO4 =Al 

Noselite.

SiO4=N.a2

\Al-SiO, ==A1

Al Si3 08 =Na2 +4H2O

Si 3 08 =nAl 

Leucite. Analcite.

That is, analcite and leucite become members of the garnet-sodalite 

group of minerals, and their relations to nephelite, albite, etc., natural 

and artificial, are perfectly clear. In analcite there may be admixtures of strictly analogous ortho-or trisilicate molecules; but these 

remain to be separately discovered. The ammonium salt corresponding to such a mixture, when ignited, might be expected to give the 

following reaction:

SiO,,=Am9 SiOfl

Al Si04 =Am2

>Al-Si8O8 =Al / \Al-Si3 08 =Al;

-2Am9 0=Al- -SiOq

Si,Oa =Al Si3O8 =Al

a reaction which is in harmony with our experimental results. In it 

no free silica appears; and many, if not all, conditions of the problem 

are satisfied. One difficulty, however, stands in the way of an unqualified acceptance of these formulae. Garnet, sodalite, nephelite, albite, 

etc., are but moderately attacked by ammonium chloride, and so far 

have yielded no definite ammonium derivatives. Whether this difference in behavior is constitutional or not it is hardly possible to 

say, but it must be taken into account in connection with all of the 

other evidence. We must remember, moreover, that the formulae
POLLUCITE. 21 .

are not ultimate verities to be blindly accepted. They are simply 

expressions which represent composition and a wide range of established relationships, and Avhich serve a distinct purpose in the correlation of our knowledge. Properly used, with due recognition of their 

limitations, they are helpful, and suggest possibilities of research; 

misused, they may become mischievous. They now satisfy most of 

the known conditions, and that is a sufficient warrant for their 

existence.

POLLUCITE.

On account of the general analogy between pollucite, analcite, and 

leucite, the first-named species of the three seemed to deserve some 

attention. Through the kindness of Prof. S. L. Penfield, about 10 

grams of very pure material from Hebron, Me., was put at our disposal, and three analyses of it by Wells were already on record." 

The average of these analyses is as follows:

BiOa--.----- --------.--------. .------ ---'----. 43.53

AltO........................................................ 16.37

CaO..._:..__.__;_.__._- .....,...,_ ......................... .22

Na20. ..................................................... 1.81

K2 0........................................................ .49

Li2O .............:.................................,....... .04

Cs2O............................. .......................... 36.08

E.O-...---- -.'..-- -.--.-. -..-...- --------. 1.52

100.06

Five grams of the finely powdered mineral was heated in a sealed tube 

with four times its weight of ammonium chloride to 350° during forty 

hours. Upon leaching with water 0.14 per cent of CaO, 1.28 of 

Na2 0, and 12.30 of Cs2 0 were extracted. Probably the calcium 

chloride formed contained some potassium chloride, but that point 

.was ignored as irrelevant. The air-dried residue had the following 

composition:

SiOj....--.......--........................................ 49.21

A12O3 ------------------------------------------------------- 18.32

CaO ---------------.---------------.-_--_---.-._....-_._-_--. none

Cs2O (K2O).................................................. 28.84

Na2O ........................................................ none

NH8 ............... ..... T .... ......................... 2.52

H2O........................................................ 1.91

100.80

The high summation here is due to reckoning some KC1 as CsCl. 

Of the silica in this product 2.36 per cent was soluble in the standard 

solution of sodium carbonate. After ignition, 4.13 per cent Avas 

soluble. Some silica, therefore, was split off bv heating.

" Ain. Jour. Sci., 3d series, Vol. XLI, p. 213,1891.
22 ACTION OF AMMONIUM CHLORIDE ON SILICATES. [BULL. 207.

In a second experiment one grain of pollucite was heated with 

ammonium chloride for five hours, the other conditions being the 

same as before. Upon leaching, 11.55 per cent of Cs2 0 was extracted, 

and a partial analysis of the air-dried residue gave the following data:

'SiO2 .___._....___......._.............--.....---....--:.:..... 47.87

A12O3 ----------------------------------- ------------------ 17.85

NH3 __......___ __'._...___._.............__..-....._..'........ 2.88

H,O............. ....-...-."."...-----:------.--- ---.--,-- 1.55

Alkalies (by difference)..................................... 29.90

100.00

The twp products were evidently the same, and only about onethird of the alkalies in the pollucite had been extracted. So, also, 

the ammonia taken up was only about one-third of that which was 

retained by analcite and leucite. The transformation, then, is 

merely partial, and further experimentation seems to be unnecessary, 

at least for present purposes. The analog}^ with analcite and leucite 

is far from perfect.

NATROLITE.

In a preliminary experiment upon an impure, yellowish natrolite 

from Aussig in Bohemia, we found that this species was peculiarly 

well suited to reaction with ammonium chloride. By heating with 

the reagent in a sealed tube and subsequent leaching with water, 

17.56 per cent of bases was extracted, and in the residue 8.29 per 

cent of ammonia was found. Careful work upon this species was 

therefore desirable.

. The material available for our experiments came from the wellkriown locality at Bergen Hill, N.' J., and consisted of a mass of 

slender needles densely matted together. -Part of the uniform, 

ground sample was analyzed, with fractional determinations of the, 

water, and part was used for the sealed tube experiments, precisely 

as in the research upon analcite and leucite. Three of these experiments were made, and in each case the natrolite was mixed by grinding in an agate mortar with four times its weight of dry ammonium 

chloride, after which it was heated to 350° in the sealed tube. Even 

during the grinding a slight reaction took place, and a distinct smell 

of ammonia was given -off by the mixture. With pectolite the same 

smell was perceived. The three experiments may be summarized as 

follows:

A. Heated eleven hours. Upon leaching. 14.89 per cent of soda and 1.20 of 

lime were extracted. In the residue 9.26 per cent of ananionia was found;

B. Heated -nine hours. Lieach not examined. 9.26 of ammonia in residue. 

The complete analysis of the residue is given farther on.

C. Heated three hours. 14.09 per cent of soda and 0.20 of lime were extracted. 

The residue contained 8.87 per cent of ammonia. In this instance the heating
CLARKE AND"!

STKIGEIl. J NATROLITE. 23

was relatively brief, in order to learn whether its diiratiou could be advantageously lessened. The reaction was evidently less complete than in experiments 

AandB.

In the subjoined table we give first tlie analysis of the natrolite itself, 

and then that of the leached residue from experiment B. In the latter 

we found that 0.86 per cent of silica was soluble in sodium carbonate 

solution, and that soda and lime remained corresponding to 4.61 per 

cent of the original mineral. Deducting these impurities, together with 

the 0.42 per cent of hygroscopic water, and recalculating to 100 per 

cent, we get the reduced composition of the residue. In the last 

column is given the calculated composition of an anhydrous ammoniumnatrolite, (NH4 ) 2Al2Si 3 010 . This compound has evidently been formed 

to an extent represented by over 94 per cent of the leached natrolite 

residue. The agreement between theory and even the unreduced 

analysis is practically conclusive on this point.

SiO2 . .................................

A1,O3 ..

CaO...... ............................

K,O.... ..............................

Na,O. -------------------------------

NH3 ................................I

H2 0 at 100°. .........................

Ilf) above 1 00° .......................

Natrolite 

found.

46.62

26.04

1.48

15.67

.39

10.18

100. 38

Residue 

found.

53.71

29.94

.34

.37

9.26

.42

5.94

99.98

Residue 

reduced.

53.86

30. 52

9.85

5.77

. 100. 00

(NH4 ) 2A12 

SiaO10 calculated.

54. 06

30.43

10. 14

5.37

100. 00

The fractional water determinations will be given later, in connection with similar data for scolecite "(p. 25).

It may not be superfluous to note that the water given in the last 

two columns of the foregoing table represents the difference between 

ammonia and the hypothetical ammonium oxide which has replaced 

soda. *

Two other experiments upon natrolite remain to be noticed. First, 

the fresh mineral was boiled for fifteen minutes with'a 25 per .cent 

sodium, carbonate solution; 0.72 per cent of silica dissolved. Similar 

treatment of ignited natrolite took out 0.62 per cent. No silica is 

split off by ignition. Ammonium natrolite before ignition.yielded 

0.85 per cent of soluble silica, and after ignition 0.86 per cent. Here 

again no silica had been split off from the molecule, and practically 

none was liberated by the action of the ammonium chloride upon the 

natrolite. A simple, direct substitution of ammonium for sodium 

had occurred.
24 ACTION OF AMMONIUM CHLORIDE ON SILICATES. [BULL. 207.

Heated with ammonium chloride in an open crucible, natrolite gives 

only a partial reaction. This is shown by the earlier experiments of 

Schneider and Clarke upon natrolite from Magnet Cove, Arkansas, 

from which, by a triple heating with the reagent, only 9.50 per cent 

of soda was extracted out of a total of 15.40.

SCOLECITE.

On account of the well-recognized analogy between natrolite and 

scolecite, the latter mineral seemed to be peculiarly worthy of examination. The specimen at our disposal was a mass of stout, radiating 

needles, which was collected by one of us at Whale Cove, on the island 

of Grand Manan, New. Brunswick. Scolecite, we believe, has not 

hitherto been recorded from this locality, and on this account alone 

the material deserved attention.

Three sealed tube experiments were carried out, essentially as in 

the case of natrolite, as follows:

A. Heated ten hours at 850°. 13.74 per cent of lime and 0.35 of soda were taken 

out. The residue contained 8.78 per cent of ammonia.

B. Heated ten hours at 370°. 12.97 of lime and. 0.22 of soda were extracted. 

8.48 per cent of ammonia in the residue. On account of the excessive temperature 

of this experiment, some reversion of the converted material had taken place.

C. Heated five hours at 340°-350°. Leach not studied. 8.91 per cent of ammonia 

in residue.

Analyses of the scolecite and of residues B and C are given below. 

The less perfect transformation in the case of B is evident.

Si02 ... ..................... -----------

AW ---------------------------------- --

CaO............ ...........................

Na2 0- .......'....................... ....

NH,_... ...... _......_......_..._...'..._...

H2O at 100°..... ...........................

H2O above 100° ...........................

Scolecite.

45. 86

95.78

13.92

.41

.40

13. 65

100.02

ResidueB.

53. 39

30. 51

.62

undet.

 8.48

.74

6.28

100. 02

Residue C.

53.69

30.50

.42

.29

8.91

.12

6.52

100. 45

The product of the reaction is plainly the same as that obtained 

from natrolite, and the identity in type of the two species is perfectly 

clear. This fact is further emphasized by an experiment upon the 

solubility of silica. The fresh scolecite gave up 0.36 per cent of silica 

to sodium carbonate solution, and the ignited mineral yielded only 

0.50 per cent. Again, natrolite and scolecite behave in the same way.

Upon both minerals fractional determinations of the water were 

made, and the amount lost at each temperature was noted. The
CLARKE 

STETGER

S AND"] 

1EH. J

SCOLECITE. 25

results, expressed in percentages of the original minerals, were as 

follows:

Temperature.

100°.-........ .................._:.-..._..-------.

i8o°.................................. .............'.:.

250°. ........................................ .:.....--

350° - . ..... ...

Incipient redness ---.-.---..-..-.-...-.--.-.--.--..-.-

Fiill rednessl _ .......................--...-....-.:--...

Over blast. . ........--...-.-........--.----.--.---.---

Water lost.

Natrolite.

0.39 

.40 

.37 

8.51 

.72 

.12 

.06

10.57

Scolecite.

0.40 

.52 

4.76 

.55 

7.72 

.04 

.06

14.05

Scolecite contains one more molecule of water than natrolite, and 

that amount, one-third of its total, seems to go off at a lower temperature than the other two molecules. Otherwise the two series of experiments are probably not far apart, and they indicate that the water 

is in neither case constitutional. The same conclusion is suggested 

by the existence of the anhydrous ammonium compound, the three 

formulae being as follows:

Scolecite ....................................... CaAl2Si3010 . 3H2 0

Natrolite ....................................... NaaAl2Si3O, 0 . 2H,O

Ammonium natrolite ............................ (NH4 ) 2Al2Si3O10

The parallelism is complete; and all three compounds are evidently 

salts of an acid, H8Si 3O]0 , Avhich is probably orthdlirisilicic acid, 

Si3 02 (OH)8 . The relations of this acid to its anhydrides will be considered later.

PREHNITE.

In a former bulletin upon the constitution of the silicates," one of 

us attempted to show that natrolite, scolecite, and prehnite were 

similar in chemical structure, provided that all or part of their Avater 

was regarded as constitutional. The formulae then assigned were as 

follows:

Scolecite ........................... r .......... Al2 (SiO4 ) 3CaH4 . H2O

Natrolite..............._....................-. Al2 (SiO4) 3Na2H4

Prehnite..................................... Al2 (SiO4 ) 3Ca2H2

Two of these formulae must now be abandoned, because of the experimental evidence which we have obtained, but the prehnite remains 

to.be considered.

nClarke, F. W., Bull. U. S. Geol. Survey No. 125, p. 45,1895.
26 ACTION OF AMMONIUM CHLORIDE ON SILICATES. [BULL. 207.

The material chosen for examination was an old specimen of prehnite from Paterson, N. J. The analysis of it, with fractional water 

determinations, is given below:

SiOj.. ...............'............. ..----------------------- 42.31

A12O8 --_---.__--.-__----.---------------- --.---------------- 19.95

Fe2O3 ------------------------------------------------------- 6.20

FeO ----_----.--------.--------------..-._-'----_---_----,.._ none

CaO.-.-....-....-.....-.-----..---....-..----....-.-..-.- 26.63

H2O..----------..----------.----- --.-.---....--.---...----- 5.02

100.11 

Fractional water.

At 100° .....................................^......*......... 0.21

At ISO0 ....--.-.-------....-------.---------------- -- .18

At 250°............ .......................^.............. .10

At 350°..-.----.-----.---------------------..-,------.-. ----- .11

Incipient red heat. .............................................. .28

Full red heat..._._..-._----.-----.---------------.--.---.--. 4.05

Over blast..-.--..-----.-.----------.--.-----------..---..-..-. .09

5.02

With sodium carbonate sulution, 0.38 per cent of silica was extracted from the fresh mineral. From the ignited prehnite, 1.22 per 

cent was taken out. Very little silica, therefore, is liberated ~by ignition.

Two determinations were made of the action of ammonium chloride, 

as follows:

A. Heated eight hours.. On leaching with water, 1.31 per cent of lime and 0.17 

of alumina dissolved.

B. Heated twelve hours. 1.41 per cent of lime was extracted, and in the washed 

residue 0.22 per cent of ammonia was found.

Prehnite, therefore, differs widely from natrolite and scolecite in 

its behavior with ammonium chloride. Very little action takes place, 

even upon long heating to 350° in a sealed tube,, and practically no

ammonia is absorbed. The water is more firmly held than was the 

case with the other two minerals, and is almost certainly to be regarded 

as constitutional. The orthosilicate formula for prehnite is unaffected by these results, and may stand as fairly probable. Prehnite 

can not be correlated with natrolite and scolecite on any basis of 

similar chemical structure.

THE TRISILICIC ACIDS.

We have already shown that natrolite and scolecite are probably 

salts of an orthotrisilicic acid, H8S3O10 , an acid which is not particularly well known. As it has interesting relations to other compounds, 

some discussion of its constitution and its derivatives may not be out 

of place here.

The general theory of the silicic acids is extremely simple. Silicon 

being a quadrivalent element,'its normal acid, the orthosilicic, is
CLARICE AND"] 

. STE1GEK. J THE TEISILICIO ACIDS. 27

Si(OH)4 . From this, by successively eliminating two molecules of 

water, two anhydrides may be derived,, thus:

Orthosilicic acid. .................................... _Si(OH) 4

First anhydride, metasilicic acid ....................._O=Si (OH) 2

Second anhydride, silicon dioxide -....-..-..---.-....-. 0=Si=O

These acids, containing one atom, of silicon each, may be called the

monosilicic acids, and some of their salts are perfectly well known.

 Olivine and anorthite, for instance, are orthosilicates, while the true

metasilicates are represented by talc and pectolite. The evidence in

the case of the last-named mineral will be presented later.

When two molecules of orthosilicic acid coalesce, with elimination 

of water, an orthodisilicic acid is formed, and this is the first member 

of another series, as follows:

SiEE(OH) 3

0

Si=(OH) 3 

Orthodisilicic acid.

Si=(OH) 3

0

O=Si-OH

Metadisilicic acid.

0=Si-OH

0

O=Si-OH

Pyrosilicic acid.

To the first and third of these acids various minerals correspond. 

The second acid, however, is a polymer of metasilicic acid, but differs 

from the latter in its possible derivatives. When an acid metasilicate 

is heated silica is set free, but in the case of a metadisilicate this 

would not necessarily occur. Possibly leucite and analcite may be 

metadisilicates, although the evidence so far presented does not support this view. The possibility, however, we are compelled to recognize as one which might ultimately be verified.

With the coalescence of three orthosilicic molecules a series of trisilicic acids begins, and one of these forms salts the feldspars which 

are the most abundant compounds existing in the mineral kingdom. 

The acids of the series are these:

Si=(OH) 3

O

Si=(OH) 2

O

Si=(OH).

O

Si=0

O

Si=(OH) 3

O

Si=0

O

0=Si-OH

O

Si=0

O

Si=(OH) 3 Si=(OH), 0=Si-OH O=Si-OH 

Orthotrisilicic acid. Metatrisilicic acid. Trisilicic acid. Third anhydride.
28 ACTION OF AMMONIUM CHLOEIDE ON SILICATES. [BULL. 207.

The third anhydride represents an acid to which no known salts 

correspond. One step further and we have a fourth anhydride, Si3 06 , 

or empirically Si02 , which may or may not be the true formula of 

quartz. Quartz is undoubtedly a polymer of Si02 ; its most frequent 

associates are trisilicates the feldspars and hence the formula Si3O6 

has a certain degree of plausibility. This suggestion, however, is 

purely speculative and has no definite scientific value. Its validity 

.would be most difficult to establish.

From the first of these trisilicic acids natrolite and scolecite appear 

to be derived. If we ignore the "zeolitic water," which is not a part 

of the essential silicate molecule, the two compounds may be formulated thus: .

Si~O, = Al Si = Os =Al

O

Natrolite. Scolecite.

So far, no other salts of this acid have been clearly identified.

The second acid of the series, like the second of the disilicic acids, 

is a polymer of the ordinary metasilicic compound. It is well understood that many so-called metasilicates are not representatives of the 

simple acid H2Si 03 ; some of them are mixtures of orthosilicates with

salts of the third acid in this group, H4 Si 3 08 ; others may be derived 

from polymers like that which is now under consideration. For 

example, anhydrous aualcite and jadeite are both represented by the 

empirical formula NaAlSigO,;, but they diifer widely in density, in 

solubility, and doubtless also in crystalline form. One molecule, 

then, is much more condensed than the other. If analcite should 

prove to be a metadisilicate, then jadeite may be its equivalent in the 

trisilicic series, or it may belong with some still higher polymer. The 

possibilities are many, but to establish any one of them by proof 

would demand more evidence than is yet in our possession.

The third member of the trisilicic series is the most important of 

all, for among its salts are the two feldspars, albite and orthoclase, 

which together make up fully one-half of the solid crust of the earth. 

It is also noteworthy from the fact that its formula can be so written
CLARKK AND"] QTTT TITTT? 9Q STJ3IOKK. J STILBI1E. 4V

as to represent tAvo isoineric forms, to which distinct salts probably 

.correspond. The two formulae are as follows:

Si==(OH)s O=Si OH

O

and Si=(OH)». 

O

i

L

O-=Si OH O = Si OH;

and their significance is clear when \ve remember that the ordinary 

trisilicates are commonly dimorphous. Thus Ave have orthoclase and 

soda orthoclase, monoclinic; and albite and microcline triclinic; one 

pair perhaps belonging to one isomer, the other to the other. The 

rare minerals eudidymite and epididymite, which are also isoineric 

trisilicates, further illustrate the same conception; but we can not as 

yet assign either compound distinctly to either formula.

By an extension of the process herein developed, which is by no 

means neAv, higher poly silicic series may be formulated. Since, however, such acids correspond to no definitely known salts, to write their 

formulas would be a useless exercise of the imagination. Beyond the 

trisilicic acids we enter the region of the unknown.,

STILBITE.

The specimen selected for study Avas a nearly white, typical example from Wassons Bluff, Nova Scotia. The analysis and the fractional 

water determinations were as follows:

SiOa -.--,---------...-------.--.--.-----.. ................. 55.41

A1A ---------- ----..--.--.--------.----.------------.--.-- 16.85

FeA--------------------------------------.----------------- -18

MgO .................. ...................................... .05

CaO........................................................ 7.78

Na,O___._..............................:.....-.............. 1.23

Hj,0..................... .................................... 19.01

100.51 

Fractional water.

At 100°........................ . ....'. ..................... 3.6'0

At 180°-.---...........:.--.............--...-............-- 6.46

At250°..................................... ................ 3.80

At 350°............................................... ...... 2.10

Low redness.-........---... ._._.-.-...-..._-.._._______..__ 2.95

Full redness................................................. .06

Over blast................................................... .04

19.01
30 ACTION OF AMMONIUM CHLORIDE ON SILICATES. [BULL. 207.

On boiling with sodium carbonate, 1.37 per cent of silica went into 

solution. After ignition, only 1.03 per cent was obtained. No silica, 

therefore, is split off when stilbite is ignited. If the mineral were a 

hydrous acid inetasilicate, H4CaAl2Si6O18 .4H2 0, as has been assumed 

by some authorities, one-third of the silica should have been set free. 

Hence the metasilicate formula is to be regarded as unsatisfactory. 

The evidence here presented counts for something against it.

Two samples of the ammonium chloride derivative were prepared. 

In leaching with water the insoluble residue was washed until the washings gave no reaction for chlorine. The chlorine shown in the subjoined analyses is, therefore, [present in an insoluble form and not as 

adhering ammonium chloride. Dried at 50° the two products gave 

the following composition:

Si02 . .................................................

A12 0,-- --------------------------- ------------------ .-

CaO. ........................ ..'.......................

NasjO................ ............................. ....

NH8 _. ......................................... ......

H2 0... ..._...-.--... .-----.........;.............

01

Less O. ---.----.--------------..*-----------..._.--._.

A.

60.80

18.36

1.86

.08

5.12

12.96

1.81*

100. 49 

.29

100. 20

B.

60. 67

18.25

1.46

.15

5.13

13.91

1.04

100.61 

.23

100. 38

Sample B was further examined as to the presence of soluble silica, 

and 1.52 per cent was found. After ignition, only 1.62 per cent went 

into solution. These results conform to those obtained with the original stilbite, and tend to show that the ammonium derivative is a compound of the same order. In the case of the unignited substance the 

residue remaining after the removal of soluble silica was thoroughly 

washed, and then examined for alkali. It was found to contain 9.30 

per cent of soda, which shows that the ammonium salt had been transformed back into the corresponding sodium compound.

From the foregoing facts it is clear that stilbite, like the zeolites 

previously studied, is converted by the action of ammonium chloride 

into an ammonium salt. That is, sodium and calcium are removed 

as chlorides, ammonium taking their place to form ammonium stilbite. 

The reaction, however, is less complete than it was in the cases of 

analcite arid natrolite, but whether this is due to a greater stability of 

the stilbite molecule or only to a different degree of fineness in the 

powder upon which the operations were performed, we can not say. 

Neither have we any explanation to offer of the retention of chlorine
STILBITE AND HEULANDITE. 31

by the ammonium derivative. Although the amount of chlorine is 

small, it needs to be accounted for.

If we discuss the composition of the stilbite and of its ammonium 

derivative, the relations between them become very clear. Neglecting the water as "zeolitic," to use Friedel's phrase, and, therefore, 

as not a part of the chemical molecule, and also rejecting the 1.37 per 

cent of soluble silica as probably an impurity, the ratios derived from 

the analysis give this empirical formula for the mineral:

Na40Ca140Al332Si90tO24G0 .

This corresponds to a mixture of ortho- and trisilicates in which 

Si 3 08 :Si04 :: 286:43; and uniting these radicles under the indiscriminate symbol X, we have, as a more general expression,

N a40Ca140 A1332 X32G ; 

or combining monoxide bases,

"R" AV 1CO'/;V1 Al 332^"VV 329J

which is essentially R"A12X2 . Since the Si04 groups are practically 

equal in number to the sodium atoms, the stilbite is probably a mixture, very nearly, of NaAlSiO,, and CaAl2 (Si3 08 ) 2 in the ratio of 1:7 

This is in accordance with the well-known theory of Fresenius as to the 

constitution of the pliillipsite group, to which stilbite belongs. Stilbite 

is mainly a hydrous calcium albite, commingled with varying amounts 

of corresponding orthosilicates of soda and lime.

For the ammonium derivative similar relations hold. Taking analysis ,"B" for discussion, rejecting soluble silica and chlorine as impurities, and neglecting all water except that which belongs to the supposable ammonium oxide, the ratios give this formula:

(NH4 ) 301Na4Ca2GAl358Si 985 02«84- 

Uniting sodium and calcium with ammonium, this becomes

R'S57Al358 (Si3 08 ) 314 (Si04 ) 43 ; 

or, more generally,

R 357A] 358X3g7 , = 1:1:1.

The derivative, therefore, is a compound of the same order as the 

original stilbite, with the ratio of 1: 7 still holding.between the ortho 

and trisilicate groups. This conclusion, however, ignores the presence of chlorine, and is, therefore, inexact to some extent. We are 

not dealing with ideally pure compounds.

HEULANDITE.

Pure, white heulandite from Berufiord, Iceland, was the material 

taken for investigation. Upon boiling with sodium carbonate, 1.73 

per cent of silica went into solution. From previously ignited heulandite, only 1.14 per cent was extracted. No silica, therefore, was 

liberated upon ignition, and a hydrous metasilicate formula for the 

mineral seems to be improbable. Only one lot of the ammonium
32 ACTION OF AMMONIUM CHLORIDE ON SILICATES. [BULL. 207.

chloride derivative was prepared, and its composition, together with 

that of the heulandite, is-given below.

Si08 --.---- -- -- - .-

Al O

MgO.------..--------------.----.---------- -..-----.

CaO .................................................

SrO..---.-----------.-----.------- ------------

Na2O ................................................

K2 0-.--. --------------------------------------------

MTT

HgOatlOO" ...........................................

H2O above 100P - --------------------------------------

Heulandite.

57. 10

16.82

.07

6.95

.46

1.25

.42

3.61

13.00

99. 68

Ammonium 

salt.

61.24

18.00

2.56

I .60

4.42

I 13.63

100. 45

Here, again, we have the same kind of transformation as before, 

but rather less complete than in the case of stilbite. That the ammonium taken up is equivalent to the bases removed is shown by a study 

of the ratios. Ignoring water and the soluble -silica, the heulandile 

ratios are as follows :

K 48-t*' 130-"-^330^5l ^'

or, uniting bases,

Again simplifying, this becomes

T?" -^ 154Ai Al 330A~V 324J

or very nearly 1:2:2, as in stilbite. 

Similarly discussed, the ammonium salt gives the ratios

K, 270*-'a46Al3g2al102 1 Oa746 ,

equivalent to

 & 362^1353X353, or 1 : 1 : 1.

In both cases the orthosilicate molecules are few, and the compounds approximate to trisilicates very closely.

CHABAZITE. ,

Characteristic flesh-colored crystals from Wassons Bluff, Nova 

Scotia. The analysis and fractional water determinations are 

SiO2 . ........................................................ 50. 78

A12O3 - .................................. ..................... 17.18

Fe2O3 - -------------------- ------------------------------ .40

MgO ............................. ........:................. .04

CaO.. ........................ .............................. 7.84

NajO- ----------------------------------------------------- 1-28

K2O ----.------------.--------.--:.----------------.--.-. .73

H2O ............ ------ ....................................... 21.85

100.10
CLAKKlt AND") 

STBIG-KU. J CHABAZITE. 33

Fractional ivater.

At 100° 

At 180°

5.22

5.70

At 250°...................................................... 3.92

At 350°.................................... ......_ -....___... 2.36

Low redness. ....-.....----.......-.-.-.-....... ..-..--....... 4.51

Full redness...-..-.....-........--.-.....-....--....-.....,.. .-13

Over blast.................. .................................. .01

21.85

The unignited mineral, upon boiling with sodium carbonate, gave 

0.86 per cent of soluble silica. After ignition only 0.53 per cent was 

soluble. Here again no silica is liberated by calcination, and metasilicate formulae may be disregarded.

Two samples of the ammonium chloride derivative were prepared, 

which after thorough washing were dried at 40° to 50°. As in the 

case of stilbite, small quantities of chlorine appear in the compound, 

not removable by washing. The amount of change effected is also 

somewhat less than with stilbite, and about the same as with heulandite. The analyses of the two samples are subjoined, with the remaining alkali all reckoned as soda:

SiO»... ...............................................

A1A ................................................

CaO .................................................

Na2 0(K,0)-_ ..........................................

"NTTT

H80. .................................. ...... ......

Cl. ................-................- .-----.-.-..

Less O '.......^. ......................................

A.

55.88

19.15

2.25

.35

4.64

16. 57

.95

99.79 

.21

99.58

B.

56.09

19.49

2.01

.24

4.83

16.01

1.35

100. 02 

.30

99. 72

In B, 1.50 per cent of soluble silica was found. After ignition this 

was reduced to 1.12 per cent. No liberation of silica accompanies the 

splitting off of water and ammonia.

Upon studying the molecular ratios for chabazite and its derivative, 

relations appear precisely like those found for stilbite and heulandite. 

For chabazite itself, rejecting water and the 0.86 per cent of soluble 

silica, we have

 " 58C%iiAl 340 k51 832O2344,

or, consolidating soda with lime,

Ca170A]340 (Si3O8 ) 246 (Si04 )94.

9506 No. 9.07 02 3
34 ACTION OF AMMONIUM CHLORIDE ON SILICATES. [BULL. 207.

. One step further and this becomes

Ca170Al340X340=l: L: 2.

Treating derivative " B " in the same way, and ignoring chlorine as 

an unexplained impurity, the analysis gives

(NH4 )284Na8Ca35Alg82 (Si3O8 ) 266 (SiO4 )lla ; 

or, consolidating bases as before,

R'363A1382X378 =1:1:1 nearly.

The assumption of commingled ortho- and trisilicate molecules conforms to Streng's theory of the constitution of chabazite.

THOMSONITE.

The compact-fibrous variety from Table Mountain, near Golden, 

Colo. Analytical data as follows:

SiO,.......... ............................................. 41.18

A12O3 -------------------------------------------- ----------- 29.58

CaO,.................... .................................. 11.25

-----...-----..-.. ................................... 5.31

-.................................................... 13.13

Fractional water.

100.40

At 100°............................:......................... 1.01

At 180°------------------.--.----.--....-----.......__..:..___ 1.44

At 250°...................................................... 1-05

At 350°...................................................... 3.90

Low redness-.................................. .............. 5.65

Over blast-.................................................. .08

13.13

Before ignition the mineral yielded 0.45 per cent of silica to sodium 

carbonate solution. After ignition 0.68 per cent was soluble. The 

difference is trifling.

Two samples of the ammonium chloride derivative were prepared. 

In A the heating was only to 300°, in B to 350°. Analyses of the 

leached products gave the following results:

SiO, .................. ..-... ..............___.-.__.

Al O

CaO .................................................

Na2O-- .............. ....:.......................

NHS ............... ...-.....:...... ........... 

Hf). ..................................... ..^... ......

A.

42. 41

30.50

10.00

2.63

2.45

11.96

99.95

B.

42.65

31.34

9.23

2.48

2.67

11.81

100.18
CI 8TBiOKi D ] THOMSONITE AND LAUMONTITE. 35

In A, 1.80 per cent of soluble silica was found.

In this case the amount of change is very much less than with the 

zeolites previously examined. Little lime was removed, and only 

about half of the soda. Both samples were prepared with six hours 

of heating in the sealed tube, and it seemed to be desirable to determine whether a more prolonged treatment would produce any greater 

effect. Accordingly a third lot of thorn sonite was mixed with ammonium chloride and heated in a sealed tube to 350° for twenty-four 

hours. The leached product contained 3.40 per cent of ammonia, a 

d istinct increase over the other findings, although the amount of transformation into an ammonium salt was still only moderate.

We have already seen that stilbite, heulandite, and chabazite 

approximate more or less nearly to trisilicates in their composition. 

Thomsonite, however, is essentially an orthosilicate, with variable 

admixtures of trisilicate molecules. In the example under consideration, ignoring water and soluble silica, the molecular ratios give this

formula :

Na178Ca201Al580 (Si8O8 ) 50 (SiO4 ) 528 ; 

or, condensing,

R"287A1380X578 =1 : 2 : 2.

Here the acid radicles are ten- elevenths orthosilicate. Ammonium 

derivative A, similarly computed, gives first 

(NPI4 ) 144Na84CamAl598 (Si3O8 )41 (Si04 ) 554 ; 

or, uniting univalent bases with lime,

the fundamental ratios being practically unchanged.

It will be observed that in all of these computations of formula? we 

have assumed that all the water is "zeolitic;" that is, independent 

of the true chemical molecules. This question, however, needs to be 

separately investigated for each' individual species. While the 

assumption is valid for some of these minerals, it is not necessarily 

valid for all. The real chemical differences between the zeolites are 

yet to be determined; our work merely proves that ammonium compounds are formed, completely in some cases, partially in ethers. 

The research should be extended to cover all the zeolites; but this 

task we must leave to other investigators.

LAUMONTITE.

Upon this species only one rather crude experiment has been tried, 

and that upon material of unknown origin. The mineral was heated 

with ammonium chloride in a sealed tube as usual, and then leached 

with water. 4.51 per cent of lime and 0.35 of soda were extracted, 

and in the residue 3.95 per cent of ammonia was found. Laumontite, 

therefore, behaves much like the other zeolites, and is only partially 

transformed into an ammonium, compound.
36 ACTION OF AMMONIUM CHLORIDE ON SILICATES. [BULL. 207.

PECTOLITE.

The pectolite which was chosen for examination was the well-known 

radiated variety from Bergen Hill, N. J. The mineral was in long 

white needles, and apparently quite pure, but the analysis shows 

that it contained some carbonate as an impurity. Enough of the 

material was ground up to furnish a uniform sample for the entire 

series of experiments, and the work properly began with a complete 

analysis. The results obtained are as follows:

SiO2 _. ...................... ................................. 58.84

AltOa ........................................................ .33

CaO--....................................--.,-............... 33.23

MnO.........................................'................ .45

Na^>........-.......\........................................ 9.11

H,O-.......................... ...........................".. 2.97

CO, ......................................................... .67

100.10

Fractional water. 

At 105°....................................................... 0.27

At 180°.................. .................."I.................. .16

At 300°....................................................... .22

At redness..................................................... 2.32

2.97

All of the water was given off at a barely visible red heat, and the 

figures show that practically all of it is constitutional a fact which 

perhaps hardly needed reverification. The analysis gives the accepted 

formula for pectolite,

HNaCa2Si3 09 .

Does this represent, as is commonly assumed, a true metasilicate? 

If it does, we should expect that ignition would split off silica proportional to the acid hydrogen, or one-sixth of the total amount. To 

answer this question several portions of the pectolite were sharply 

ignited, to complete dehydration, and then boiled each for fifteen 

minutes with a solution of sodium carbonate containing 250 grams to 

the liter. In the extract so obtained the silica was determined, and 

the three experiments gave the following percentages:

8.96

8.67

8.42

Mean, 8.68

One-sixth of the total silica is 8.89 per cent, and the experiments, 

therefore, justify the original expectation. The belief that pectolite 

is a metasilicate is effectively confirmed.

Upon the unignited pectolite the sodium carbonate solution has a 

slow decomposing action, both silica and bases being withdrawn. In 

two experiments fifteen minutes of boiling extracted 2.07 and 2.55 

per cent of silica, and by a treatment lasting four days 4.80 per cent
CLARKffl AND"] 

STKIGER. J PECTOLITE. 37

was taken out. With water alone similar results were obtained, the 

action being so rapid, although relatively slight, that pectolite, moistened, gives an immediate and deep coloration with phenol 

phthalein. By boiling the powdered pectolite with distilled water 

alone, 1.65 per cent of silica was brought into solution, and the 

ignited mineral, similarly treated for fifteen minutes, gave 1.78 per 

cent. The extraction in these cases is really an extraction of alkaline 

silicate, as the two following experiments prove. In A the unignited 

pectolite was boiled for fourteen hours with distilled water, and in 

B the mineral after ignition was subjected to like treatment for four 

hours. The dissolved matter in each case was determined, with the 

subjoined results:

Extracted.

SiO2 . ........................... ......................

CaO.... ...............................................

Na2O ................................................

A.

2.98

.30

.81

4.09

B.

3.03

.10

1.50

4.63

In A no simple ratio appears, but in B the extracted silicate approximates very nearly to the salt Na2Si2 05 . In each instance the ratios 

vary widely from those of the original mineral, showing that actual 

decomposition and not a solution of the pectolite, as such, has occurred.

Schneider and Clarke/ in their first experiments upon the ammonium chloride reaction, treated pectolite from Bergen Hill three 

times successively with the reagent and then leached out with water. 

In the solution 20.50 per cent of lime and 6.95 of soda were found, 

showing that a very considerable decomposition had taken place, 

but the residue was not examined. In a preliminary experiment 

by the sealed tube method we found that 20.72 per cent of lime and 

6.46 of soda were taken out, while 1.44 per cent of ammonia was 

retained by the residue. That is, two-thirds of the bases, approximately, had been converted into chlorides by the reaction. The open 

crucible and the sealed tube gave essentially the same results, although 

the retention of ammonia was not noticed by Schneider and Clarke.

In order to obtain further light upon pectolite we continued bur 

experiments with the sealed tube method, and have obtained very 

variable results. All of the heatings with ammonium chloride were 

conducted at 350°, and the pectolite used was from the same Bergen 

Hill specimen which served us for our previous work. Our data are 

as follows, including for convenience of comparison the preliminary 

experiment which was cited above:

A. Heated six hours. On leaching, 20.72 per cent of lime, 6.46 soda, and 0.11 

alumina dissolved. The residue contained 1.44 per cent of ammonia.

"Bull. U. S. Geol. Survey No. 113, p. 34, 1893.
38 ACTION OF AMMONIUM CHLORIDE ON SILICATES. [BULL. 207.

B. Heated six hours. 20.10 per cent lime and 5.80 of soda extracted. 1.45 per 

cent ammonia in the residue. The residue was also examined for silica soluble 

in 25 per cent sodium carbonate solution (on fifteen minutes boiling), and 43.38 

per cent was found.

C. Heated six hours. Soluble portion neglected. The residue contained 2.23 

per cent of ammonia and 61.79 per cent of soluble silica. The full analysis of 

this residue is given later.

D. Heated ten hours. A complex breaking up of the pectolite took place, and 

leaching with water extracted the following percentages:

Si02 . 

A1A 

CaOMnO. 

Na2O

5.43 

.22

28.20

.23

8.29

The residue from this leaching contained 39.63 of soluble silica, but ammonia 

was not determined.

These results are so irregular that definite conclusions can hardly 

be drawn from them. A and B agree fairly with each other, and 

also with the earlier work of Schneider and Clarke.' C contains more 

ammonia, but differs widely from B as to the amount of soluble silica 

in the residue. D, which represents a long heating, indicates a more 

complete reaction than was observed in either of the other cases.

An ammonium compound, however, is evidently formed during the 

reaction, although its precise nature can not be determined from the 

evidence now in hand. Something may be inferred from the following figures, which are to be summarized thus: First, we reproduce 

from our earlier paper the analysis of the pectolite itself. Secondly, 

we give the analysis of the insoluble residue obtained in experiment 

C. The third column of figures is obtained by subtracting from the 

second column 61.79 of soluble silica and 1.18 of hygroscopic water, 

and recalculating the remainder to 100 per cent. The fourth column 

contains the molecular ratios calculated from the third.

SiO2 . ........ .........................

AI n

CaO.. ....... .......................I

MnO-. ...... .........................

Na2O... ..............................

NH3 ......'...........................

HjO at 100°...... .....................

H2O above 100°..... .. ..--..-..-..-.-.

CO,........-..,.-.....--....--....-..

Pectolite.

53. 34

.33

33.23

.45

9.11

27

2.70

.67

100. 10

Residue 

found.

75. 98

.08

9.56

.24

1.84

2.23

1.18

9.47

100. 58

Residue 

reduced.

37.74

.19

25. 43

.63

4.89

5.93

25. 19

100. 00

Ratios.

0.629

.002

.454

.009

.079

.349

1.399
WOLLASTONITE AND APOPHYLLITE. 39

These ratios roughly suggest the formation of a salt approximating 

in composition to the formula R'2Ca2Si 3 09 .6H2 0, in which. R/ is about 

two-thirds ammonium and one-third sodium. The large amount of 

water found was doubtless absorbed during the process of leaching. 

Pectolite itself has the formula ]STaHCa2Si3 09 , so that the existence of 

a hydrous ammonium pectolite is indicated; a conclusion which is 

probable but not proved. The reaction between pectolite and ammonium chloride is possibly simple at first, but followed by or entangled 

with secondary changes which obscure the results. The experiments 

are interesting, however, as showing how widely pectolite differs from 

the other minerals which we have studied, as regards the ammonium 

chloride reaction.

WOLLASTONITE.

The only data relative to the action of ammonium chloride upon 

wollastonite are those given in the original paper by Schneider and 

Clarke, but on account of the close relationship between this species 

and pectolite it seems desirable to reproduce the record here. The 

mineral studied was from Diana. N. Y., and it had the subjoined 

composition :

SiO. -- --.-..----------. -------------------------------- 50.05

CaO-. ...................................................... 47.10

Na2O- ...----..---.-.--.-.--------------------------.----.-- undet.

MgO ....................................................... .09

HaO. ....................................................... .45

98.82

After two heatings with ammonium chloride in an open crucible, 

36.98 per cent of lime became soluble in water. In other words, a 

very notable decomposition had occurred, as in the case of pectolite. 

Since wollastonite is an anhydrous mineral, this result shows that 

the reaction does not depend upon the presence of hydroxyl.

APOPHYLLITE.

Upon this species only one rather crude experiment was made, and 

that with material of unknown locality. Heated with ammonium 

chloride in a sealed tube, it gave up, on leaching with water, 21.59 

per cent of lime and 5.18 of potassa. The residue contained only 

0.79 per cent of ammonia. Evidently the mineral, like pectolite and 

wollastonite, is largely decomposed by the reagent; but it is uncertain 

whether any regular ammonium compound is formed. It must be 

remembered that apophyllite sometimes contains small quantities of 

ammonia, and hence it seems that a more complete investigation of it 

is desirable.
40 ACTION OF AMMONIUM CHLORIDE ON SILICATES. [BULL. 207.

DATOLITE.

The compact, porcelain-like datolite from Lake Superior. This 

was heated in a sealed tube with ammonium chloride in the usual 

way. Afte"r leaching the product with water, the washed residue contained 91.09 per cent of silica and 1.17 of ammonia. Evidently the 

datolite molecule had been thoroughly broken down, with nearly 

complete removal of the bases and the boric acid. The significance 

of the retained ammonia, however, is not clear.

ELJEOLITE.

On account of their interest as rock-forming minerals, the three 

species nephelite var. elseolite, sodalite, and cancrinite were studied 

consecutively and with some reference to one another. The elaeolite 

was the characteristic material from the elseolite-syenite of Litchfield, 

Me., and had the following composition:

SiO2 ......................................................... 45.91

A12O3 -------------------------------------------------------- 31.14

FeA------------------------------------------------------- -34

FeO... ...................................................... .23

CaOl.----- ---------.-.--...--..----...-....---..----.--..- .33

Na2O........................................................ 14.60

KgO................ ....................................... 5.60

H2O at 100°.................................................. .47

H2O above 100°............................................... .93

CO.......................................................... .40

99.95

Five grams of mineral were thoroughly mixed with 20 grams of 

ammonium chloride by long grinding in an agate mortar, and then 

heated for six hours in a sealed tube to 350°. Even during the grinding a strong smell of ammonia was noticeable, and upon opening the 

sealed tube after heating, a slight pressure of ammonia gas was 

observed. On extraction with water the following bases passed into 

solution:

FeA-AlA---------------------.. --------------------------- 0.29

CaO......................................................... .07

Alkalies (calculated as soda)....--..............----.....-..- 2.10

The residue from, the leach water was dried at 50°, and then found 

to contain 0.92 per cent of ammonia. These figures confirm those 

obtained in a much less careful preliminary experiment, and show 

that elseolite is but slightly affected by the reagent.
OT..ABKT: AND")

STBIOEB. J

CANOEINITE. 41

CANCRINITE.

The material studied was the well-known bright yellow cancrinite 

from Litchfield, Me., and an analysis of it gave the following results:

810,-. -.------.---------.-----.-------.----.------ 36.19

A12O3 ---..--.--..-_.. -..-..--.-.--- ....--...-----.-.-- 29.24

Fe.,O« .....................................^.................. trace

CaO

Na2O

K2O_.

H20.

CO2 ..

4.72

19.20

.14

4.15

6.11

99.75

Upon boiling the powdered mineral for fifteen minutes with the 

standard solution of sodium carbonate, 0.55 per cent of silica went 

into solution. After ignition, only 0.32 per cent was soluble. No 

silica, therefore, had been split off by heating.

With ammonium chloride two experiments were made. In each 

case the mineral was intimately ground with four times its weight of 

the chloride, and heated to 350° in a sealed tube for four hours. 

During grinding a strong smell of ammonia was noticed, and still 

more was given off when the tubes were opened. The products were 

leached with water, and the thoroughly washed residues were analyzed, as follows:

SiOa ..--. -- ..-.---- --. .-.-... .- 

Al O

CaO..................................................

Ni^CK+K^O).... .....................................

NH3 .................................................

H2O at 100° ...........................................

H2O above 100° ........................... L ...........

CO,. - ............................................

A.

37. 48

31.23

5.10

7.78

4.73

1.29

12.24

99.85

B.

37.51

31.98

5.30

7.53

3.77

| 14. 48

none

100. 57

In the wash water from product B, 11.73 per cent of the original 

soda was found, with no lime, and 0.16 per cent of silica and alumina. 

Somewhat less than two-thirds of the soda had been taken out. The 

lime seems to be much more stably combined, and water was taken 

up, probably in the process of leaching. The carbonic acid of the 

cancrinite had been completely eliminated.
42 ACTION OP AMMONIUM CHLORIDE ON SILICATES. [BULL. 207.

Apparently, if the product of the reaction is a definite compound, 

the effect of the ammonium chloride has been to transform the cancrinite into a zeolitic body, approximating roughly to the general formula

R'AlSiC^. H2O,

but with a small excess of the univalent bases. Analysis A, 

adjusted by rejecting the 1.29 per cent of hygroscopic water, and 

recalculation of the remainder to 100 per cent, assumes the following 

form and gives the appended ratios:

SiCv. ................................................

A^OS .. ...............................................

CaO.-..-..---...----.................-.---...-. ......

Na,O...... ............. ....'...........................

NHS ..._ .............................................

H,O.. ................................................

Analysis reduced.

38.03

31.69

5.17

7.89

4.80

12 42

100.00

Ratios.

0.634

.311

.093

127

282

.690

The substance is evidently not absolutely pure, a condition which 

might have been expected. Any closer attempt at precise formulation would therefore be useless. It most nearly resembles, among 

the products which we have obtained, the ammonium derivative of 

thomsonite.

SODALITE.

Dark-blue sodalite from Kicking Horse Pass, British Columbia. 

Analysis as follows:

SiO2 . .......................... ............................ 39.66

A1A ...... .......................................'...........' 30.09

Fej,O3 . 

CaO. .

H2OatlOO° ... 

H2O above 100° 

01............

LessO=Cl.

.31

.18

22.60

1.14

.17

.79

6.12

101.06

1.39

99.67

With ammonium chloride two preparations were made, both by 

the sealed-tube method at 350°. In A the heating lasted twenty-four 

hours; and in B six hours. From residue A, by leaching with water, 

2.96 per cent of alkali, reckoned as soda, was extracted; and from B,
CLARKE AND"

STEIGEH SODALITE AND THE FELDSPAES. 43

3.53 per1 cent. In the washed residues the following determinations 

were made, but complete analysis seemed to be unnecessary.

SiO,-.. ..............................................

AlA(FeA) ---..-- -..---.-. - ---.--

CaO-.- --...------.- ................................

NajOCKjO).. ............................. ...........

NHS ....... ............................................

CL--..-.---..-.-...-.-....-....---.-..-......

A.

39.33

31.40

.20

20. 86

.45

5.92

B.

40.00

32.34

.72

Evidently the amount of change was slight, and no definite ammonium derivative had been formed.

In one way these results shed some light upon the constitution of 

sodalite. According to Lemberg and his pupils the mineral is a double 

salt, a molecular compound of sodium chloride with a silicate like 

nepheline. If this view were correct' sodium and chlorine should be 

removed together by the action of a decomposing reagent. "We find, 

however, that about 3 per cent of soda was removed from sodalite in 

forming residue A, while practically all of the chlorine remains 

behind. So far, then, the evidence is adverse to the view just cited 

and favorable to that of Brogger, which assigns the mineral, as an 

atomic compound, to a place in the garnet group.

On the other hand, sodium chloride may be volatilized from sodalite 

by prolonged heating. Two portions of the mineral were each heated 

for four hours over a blast-lamp flame, losing 10.80 and 10.72 per cent, 

respectively. The chlorine in the mineral, 6.12 per cent, corresponds 

to 10.08 per cent of NaCl; to this must be added the 0.91 of water 

found, making a total possible loss of 11.04; per cent. In the residue 

from the first lot ignited 0.20 of chlorine Avas found, so that the volatilization of sodium chloride had been almost complete. This reaction, however, taking place at a very high temperature, may be only 

a result of metathesis, and not by any means a proof that sodium 

chloride, as such, is an essential constituent of sodalite. The evidence derived from the ammonium chloride reaction is entitled to the 

greater weight.

THE FELDSPARS.

The results which we have obtained with these important rockforming minerals are interesting only in so far as they show a trifling 

sensitiveness on the part of the,.several species.toward dissociating 

ammonium chloride. The action upon them is slight, and ammonium 

derivatives do not seem to be formed. The data may be briefly summarized as follows:

Orihoclase. From southeastern Pennsylvania, exact locality 

unknown. Quite pure cleavage masses. Heated for six hours with
44 ACTION OF AMMONIUM CHLORIDE ON SILICATES. [BULL. 207.

ammonium chloride to 350° in a sealed tube, and leached with water, 

1.52 per cent of KC1 went into solution. The residue, dried at 50°, 

contained 0.20 per cent of ammonia.

Oligoclase. The transparent variety from Bakersville, N. C. 

Treated like the orthoclase. In the leach water 0.96 per cent of lime 

and 2.71 of soda were found. The air-dried residue contained 1.47 

p.er cent of ammonia. It is barely possible that in this case an ammonium derivative may. have been produced, but the data are not positive enough to warrant any definite conclusion.

 ATbite. Well-crystallized and very pure material from Amelia 

Courthouse, Va. Treated like the two preceding feldspars. Upon 

leaching, 0.12 percent of lime and 0.84 of soda went into solution. 

In the residue, dried at 50°, 0.32 per cent of ammonia was retained.

OLIVINE.

Green, transparent pebbles from near Fort Wingate, N. Mex. 

Examined by Schneider and Clarke, who employed only the open 

crucible method.. By treatment with ammonium chloride only 0.44 

per cent of magnesia was rendered soluble in water i. e., converted 

into magnesium chloride. In view of the ready solubility of this 

mineral in even weak aqueous acids, this lack of sensitiveness to 

ammonium chloride is somewhat remarkable.

ILVAITE.

This rare mineral was found by Mr. Waldemar Lindgren at the 

Golconda mine, South Mountain, Owyhee County, Idaho. It occurs 

in jet black masses and occasional rough crystals, embedded in quartz 

or calcite, and intimately associated with two other minerals which 

appear to be garnet and tremolite! Traces of pyrite also appear. 

The specific gravity of the ilvaite, as determined by Dr. Hillebrand, 

is 4.059 at 31°.

Upon grinding the powdered mineral with ammonium chloride in 

an agate mortar, a distinct smell of ammonia was noticeable. Three 

tubes of the mixture were heated to 350°, and one exploded because 

of the liberation of gas within. Upon opening the second and third 

tubes, a strong outrush of ammonia was observed. When the contents of these tubes were leached with water, large quantities of 

ferrous chloride went into solution, which, rapidly oxidizing, formed 

a deposit of brownish hydroxide, and interfered seriously with filtration. The greater part of the lime in the ilvaite was dissolved also. 

The washed residue, containing much ferric hydroxide, was partially 

analyzed, and enough data were obtained to show that a general 

breaking down of the ilvaite molecule had been effected. Apparently, 

also, small quantities of an ammonium derivative had been formed;
CTjAKKE AND") 

STE1QEK. J

ILVAITE AND RIEBECKITE. 45

but this point is uncertain. The original mineral was analyzed by 

Dr. W. F. Hillebrand, and his analysis, contrasted with that of the 

leached residue, is here given:

SiO2 ... --..-... ...--...--....... ....................

A1A ...............................................

FeA ----------------------------------------

FeO ..........'.......................................

MnO.. ................................................

CaO.. .......................................... .-...-

MgO. ............................................... ..

Na,O..------ ---------------------------------------

NH3 . ...... ...........................................

HjOatl05°....... .......... .........................

H2O above 105° .......................................

Cl ..................................................

Ilvaite (Hillebrand).

29.16

.52

20.40

29.14

5.15

13.02

.15

.08

.15

2.64

100. 41

Residue 

(Steiger).

43.01

} 40.08

8.75

.85

2.25

undet.

imclet.

.88

undet.

tindet.

(a)

95. 82

« Small amount.

In the leached residue from the third tube 21.37 per cent of soluble 

silica was found silica which had been liberated during the reaction 

between the ilvaite and the ammonium chloride. In short, ilvaite 

behaves toward the reagent much like pectolite, and the product is a 

mixture of uncertain character. The evident instability of the ilvaite 

molecule may account for its rarity as a mineral species. Only 

exceptional conditions would favor its formation.

RIEBECKITE (?).

The results obtained with ilvaite made it desirable to study, for 

comparison, some other silicates of iron. Among these the mineral 

from St. Peters Dome, near Pikes Peak, Colorado, originally described 

by Koenig as arfvedsonite, but identified by Lacroix as near riebeckite, happened to be available. It was treated with ammonium chloride in the usual way and no presence of liberated gas was noticed 

when the tube was opened. On leaching the product with water, ferrous chloride went into solution and ferric hydroxide with some 

manganic hydroxide was deposited. In the leached mass 6.90 per 

cent of soluble silica was found, and in the wash water from the 

leaching there was 6.76 per cent of soda. According to Koenig's 

analysis the mineral contains 8.33 percent of soda, so that a large 

portion of the total amount had been extracted. There was also,
46 ACTION. OF AMMONIUM CHLORIDE ON SILICATES. [BULL. 207.

evidently, a considerable breaking down of the molecule, but no 

definite ammonium derivative had been formed. This is shown by 

the following analysis of the leached residue, which is contrasted 

with Koenig's published analysis* of the original mineral in order to 

indicate the amount of change. In the third column of figured we 

give the amount of each constituent which could be dissolved out 

from the residue by treatment with hydrochloric acid.

Si(V... ..................................

Ti02 . ....................................

Zr02 . ....................................

FeA ------------------------------------

FeO .....................................

MnO. .....................................

MgO.-._ .--..--.-.......---.....-...._ _..

CaO .

Na2O ....................................

KjO. .....................................

NH8 -.. ........ ..........................

HP--..-.----.--.---..-.-------..-.......

a. --- -- - .-.. - .

Riebeckite 

(Koenig).

49.83

1.43

.75

14.87

18.86

1.75

.41

8.33

1.44

.20

97.87

Residue 

(Steiger).

67. 54

21.28

4.94

.64

none

1 1.04

.53

3.33

trace

99.30

Soluble 

portion.

15.74

4.94

.64

.53

The residue is evidently a mixture of free silica and ferric hydrate 

with probably at least two silicates, one soluble, the other insoluble 

in hydrochloric acid. The reaction itself is noteworthy because of 

the fact that the original mineral is but slightly attacked when boiled 

with strong hydrochloric acid. . The other minerals so far studied by 

us are all easily decomposable by acids, while this one is quite refractory. The energetic character of the ammonium chloride reaction is 

thus strongly emphasized.

J5GIKITE.

Material from the well-known locality at Magnet Cove, Arkansas. 

Not absolutely pure, but somewhat contaminated by ferric hydroxide. 

This impurity is evident in a discussion of the ratios furnished by 

the analysis, but is not serious. It. does not affect the problems under 

consideration. By heating with ammonium chloride the mineral was 

only slightly changed. In the leach water from the product there

aDana's System of Mineralogy, 6th ed., p. 400.
CljAKKE AND'l 

STEJGER. _\ ^EGIBITE AND CALAMINE. 47

were 1.66 per cent (AlFe)2 03 , 0.51 CaO and 1.18 Na2 0. Analyses as 

follows: A of the segirite, B of the air-dried, leached residue.

Si02 . .................................................

Al O

FeA --------------------------

FeO. ................ ... .

MnO-. .............J..................................

MgO ............... ........................:.........

CaO .................................................

KG

NH, ----------------------------------------

HaO at 100° ..............................

H.,0 above 100° ........................................

A.

50. 45

2.76

23.42

5.26

.10

1.48

5.92

9.84

.24

.15

.40

100. 02

B.

51.83

| 25. 24

5.69

1.58

5.74

} 9..07

.26

} .90

100. 31

Of the silica in the residue 4.42 per cent was soluble in sodium carbonate solution. An ammonium derivative was not formed.

From these data we see that the three iron silicates are very differently attacked by ammonium chloride; ilvalte very strongly, riebeckite moderately, and segirite but feebly. The aegirite is the most 

stable and at the same time the 'commonest of the three. A comparison of the segirite analysis with that made by J. Lawrence Smith 

of material from the same region shows notable differences. The 

mineral evidently varies in composition, the variation depending 

upon the relative amounts of the two silicate molecules FeNaSi2 06 

and R"Si03 . Two samples taken from different parts of the same 

rock area are not necessarily identical in composition.

CALAMINE.

The simplest constitutional formula for calamine, the one which is 

generally accepted, represents it as a basic metasilicate,

Si03 =(ZnOH) a .

In this the hydrogen is all combined in one way, and so, too, is the 

zinc. In all other possible formulae, simple or complex, the hydrogen 

as well as the zinc must be represented as' present in at least two 

modes of combination; a condition of which, if it exists, some evidence 

should be attainable. Our experiments upon calamine have had this 

point in view; and we have sought to ascertain whether water or zinc 

could be split off in separately recognizable fractions. Our results, 

in the main, have been negative, and tend toward the support of the
48 ACTION OF AMMONIUM CHLORIDE ON SILICATES. [BULL. 207.

usual formula; but the data are not conclusive, although they seem 

to be worthy of record.

The beautifiil white calamine from Franklin, N. J., was selected 

for study, and gave the subjoined composition:

SiO,--.---------.-----------.-------..-------------.----- 24.15

ALA, Fe2 03 ------------------------------------------------- - 19

ZnO.---..................................................... 67.55

CaO.......................................................... .12

H2O.......... .............................................. 7.95

99. 96 

Fractional ivater.

At 100° _..___.__._ ____._._.-.._......-...._.---_-------.----. 0.27

At 180°...................................................... .22

At 250°---...------------------------------------------------ .75

At 300°....................................................... .88

Incipient red heat........ ........................-..._......- 4.46

Full red heat................................................ 1.37

7.95

Here no clear and definite fractionation of the water is recognizable, 

at least of such a character as to suggest any other than the ordinary 

formula for calamine.

Upon bailing powdered calamine with water, practically nothing 

went into solution, but by boiling with the solution of sodium carbonate 0.25 per cent of silica was dissolved. After ignition at a red 

heat, only 0.14 per cent of silica became soluble in sodium carbonate; 

and after blasting, only 0.24. In these experiments a very little zinc 

was dissolved also; but there was no evidence that any breaking up 

of the mineral into distinguishable fractions had occurred. In a hot 

10 per cent solution of caustic soda both the .fresh and the ignited 

calamine dissolve almost completely; but boiling with aqueous ammonia seems to leave the mineral practically unattacked. All experiments aiming to extract a definite fraction of zinc while leaving a 

similar fraction behind resulted negatively.

By heating with dry ammonium chloride in an open crucible, calamine is vigorously attacked and gains in weight by absorption of 

chlorine. In two experiments the mineral was intimately mixed with 

three times its weight of powdered sal ammoniac and heated in an air 

bath for several hours to a temperature somewhat over 400°. A large 

part of the residue was soluble in water, and the percentage of this 

portion, together with the percentage increase in weight, is given 

belowr :

Gain in weight .......................................

Soluble in water. . .....................................

I.

27.60

53.23

II.

25.78

67.13
CALAMINE AND PYKOPHYLLITE. 49

A conversion of calamine into the chlorhydrin Si03 (ZnCl) 2 would 

involve a gain in weight of 15.34 per cent. Complete conversion into 

2ZnCl2 4-Si02 implies an increase of 38.14 per cent. The figures given 

lie between these two, and are indefinite also for the reason that there 

was volatilization of zinc chloride.

In two more experiments the calamine, mingled with three times 

and four times its weight of ammonium chloride, respectively, was 

heated for an hour and a half to bright redness in a combustion tube. 

The zinc chloride which was formed volatilized and was collected by 

suitable means for determination. It corresponded to 59.6 and 59.0 per 

cent of the original mineral, calculated as zinc oxide, which indicates 

a nearly complete decomposition of the calamine into 2ZnCl2 +Si02 . 

The residue was mainly silica, with a small part of the zinc, about 

half of the silica being soluble in sodium carbonate solution. Here 

again no definite fractionation of the mineral could be observed.

Finally the action of dry hydrogen sulphide upon calamine was 

investigated. The mineral was heated to redness in a current of the 

gas and gained perceptibly in weight. The percentage data, reckoned 

on the original calamine, were as follows, in two experiments:

Gain in weight ............ ...........................

SiO2 soluble in Na2CO3 ...--.....-...-....-...-.-.---.--

I.

6.00

16. 45

II.

6.43

20.95

24. 12

Complete conversion of calamine into 2ZuS+SiO2 implies a gain in 

weight of 5.80 per cent, and it is therefore evident from the figures of 

the second experiment that the limit of change was approached very 

nearly. The 24.12 of sulphur taken up is quite close to the 26.53 per 

cent which is required by theory. About eight-ninths of the calamine 

had undergone transformation. Again no definite fractionation was 

detected.

The hydrogen sulphide reaction was examined still further with 

reference to the temperature at which it becomes effective. Even in 

the cold calamine is slightly attacked by the gas, but its action is 

unimportant until the temperature of 400° is approximated. Then it 

becomes vigorous and the reaction goes on rapidly. A few experiments with willemite showed that it also was attacked by hydrogen 

sulphide, but less vigorously than calamine.

PYROPHYLLITE.

The empirical formula for pyrophyllite, AlHSi2 06 , is apparently 

that of an acid metasilicate, and the mineral is therefore peculiarly 

available for fractional analysis. The compact variety from Deep 

9506 No. 207 02 4
50 ACTION OF AMMONIUM CHLORIDE ON SILICATES. [BULL. 207.

River, N. C., was taken for examination, and a uniform sample was 

prepared. Analysis gave the following results:

SiOj----.---.--.--.-.----.--- ---------.-----..--.. ---------- 64.73

Ti02 ........................................................ .73

A12O3 ----------------------------------------------------- 29-16

Fe203 ---...-_............................................... .49

MgO -....--....---...-.-.-.-.-.--..---..----..-.--....--... trace

Ignition-..--.. ......-.----.-...-...--.-.-..--...--.-,.-... 5.35

100.46

If, now, pyrophyllite is an acid metasilicate it should break up on 

ignition in accordance with the equation

2AlHSi2 06 =Al2Si3 09 +Si02 +H30.

That is, one-fourth of the silica, or 16.18 per cent, should be liberated. The mineral itself is very slightly attacked by boiling with the 

sodium carbonate solution, and in an experiment of this kind only 

0.72 per cent of silica was dissolved. Upon ignition under varying 

circumstances the following data were obtained:

Ignited ten minutes over a Bunsen burner, and then extracted with 

sodium carbonate solution, 1.51 per cent of Si02 dissolved.

Ignited fifteen minutes over a Bunsen burner, 1.89 per cent became 

soluble.

Ignited ten minutes over a Bunsen burner and then fifteen minutes 

over the blast, 2.84 per cent of silica was liberated.

These results are of a different order from those given by pectolite 

and talc, and raise the question whether pyrophyllite, despite its 

ratios, is a metasilicate at all. So far as the evidence goes, it may 

with propriety be regarded as a basic salt of the acid H2Si2O5 , and its 

formula then becomes

Si2 05 =Al-OH.

This formula is at least as probable as the metasilicate expression, 

which latter rests upon assumption alone. Still other formulae, but 

of greater complexity, are possible; but until we know more of the 

genesis and chemical relationships of pyrophyllite, speculation concerning them would be unprofitable.

By heating with ammonium chloride in an open crucible pyrophyllite is very slightly attacked. In two experiments it lost in weight 

6.17 and 6.30 per cent, respectively. The excess of loss over water is 

due, as we have proved, to the volatilization of a little ferric and 

aluminic chloride. The residue of the mineral after this treatment 

contained no chlorine, so that no chlorhydrin-like body had been 

formed. The formation of such a compound, the replacement of 

hydroxyl by chlorine, Avould, if it could be effected, be a valuable 

datum toward determining the actual constitution of the species. 

The sealed tube experiments were not attempted.
CLAHKE AND"! 

STEI.OKU. J SEEPENTINE AND PHLOGOPITE. 51

SERPENTINE.

In 1891 Clarke and Schneider published an investigation a relative 

to the action of gaseous hydrochloric acid upon various minerals. 

Among these were the three species, serpentine, leuchtenbergite, and 

phlogopite, and the remainders of the original samples were fortunately at our disposal. The analyses made by Schneider are therefore directly comparable with the new data secured by us.

The serpentine, from Newburyport, Mass., was but moderately 

attacked upon heating with ammonium chloride. Upon leaching the 

contents of the sealed tube with water, 0.18 per cent of silica and 5.23 

of magnesia Avent into solution. The washed residue and the serpentine had the following composition:

Si02 .._._...-.............-...--.-...-..------'-. --

Fefo,, AJA ------------------------------------- ------

MgO. -- .--- '-..- -- .- - ~ 

FeO_ - - - ----- . - ......

NH,.. -..---.--. .------...------.--...-..-.-.-.------.

H.O.... .......... ..............-.....--.-.-..----..-.

Serpentine 

(Schneider).

41.47

1.73

41.70

.09

15. 00

100. 05

Residue 

(Steiger).

45.42

.88

89. 54

.09

14. 01

99. 94

The leached residue contained 1.06 per cent of soluble silica. The 

amount of change effected in the mineral was evidently small, and no 

ammonium compound was produced.

In Schneider and Clarke's & paper upon the ammonium chloride 

reaction a serpentine from the river Poldnewaja, district of Syssert, 

in the Urals, was studied. By a single treatment in an open crucible 

4.93 per cent of magnesia became soluble in water as chloride. In a 

second experiment the mineral, after heating with 10 grams of ammonium chloride until volatilization ceased, Avas reheated with 10 grams 

more. Upon leaching, .1.4.30 per cent of magnesia went into solution. 

In a third trial the serpentine was thrice treated and only 10.63 per 

cent of magnesia was converted into chloride. .In the last case the 

residue was boiled with sodium carbonate solution, which extracted 

3.82 per cent of silica. The same serpentine was completely decomposable by aqueous hydrochloric acid, but only moderately attacked 

by the dry gas. The evident irregularity of these results is yet unexplained.

PHLOGOPITE.

From Burgess, Canada. The contents of the sealed tube, after 

heating, showed little appearance of change. The leach water contained magnesia. Analyses as follows:

a Bull. IT. S. Geol. Survey No. 78, p. 11,1891. 6 Bull. U. S. Geol. Survey No. 113, p. 34,1893.
52 ACTION OF AMMONIUM CHLOBIDE ON SILICATES. IBULL. 207.

SiO2 ._, ...............................................

TiO,-.. ....... ..................................... ..

A^0t.......... ........................................

FeA ................................................

FeO...... ............................................

BaO ....................................................

MgO --.-..-..-----.----..----------------. -i. ------ ..

No/).- ...............................................

KaO ... .........................................

NH....... ............................................

HaO ...................................................

F ....................................................

Less O ___-._-_-_...-.-_ _...--_-..-.-... .............

Phlogopite 

(.Schneider).

39.66

.56

17.00

27

.20

.62

26.49

.60

9.97

2.99

2.24

100. 60 

.94

99.66

Residue 

(Steiger).

45.03

,

| 15.07

24. 94

.94

8.69

.21

5.01

99.89

The residue, on boiling with sodium carbonate, gave 0.40 per cent 

of soluble silica. From these data it appears that phlogopite is somewhat attacked by ammonium chloride, but not strongly. No definite 

ammonium derivative is formed.

LEUCHTENBERGITE.

From the standard locality near Slatoust, in the Urals. When the 

contents of the sealed tube were leached with water, there passed into 

solution 0.19 per cent of alumina, plus iron, 2.10 of magnesia, and 

2.03 of lime. The residue was not completely analyzed, but the few 

determinations made contrast with Schneider's results as follows:

SiO, .... ................................. ....../r...

AI n >

Fe2 03 ----.----.-.---- -- ---.---. -- 

FeO-. ............................................... .

MgO ................ ..................'..............

CaO. ---.-------------.------------- ---- .------.-..--.

NH...... .............................................

HaO..... ........ .. .. ...,........... ......

Leuchtenbergite.

32.27

16.05

4.26

.28

29.75

6.21

11.47

100. 29

Residue

(Steiger).

32.82

4.67

.25

12.11
CLARKE AND

STKIGKKND ] LEUCHTENBERGITE AND XANTHOPHY.LLITE. 53

No definite ammonium compound was formed, and the amount of 

decomposition was small. As the lime shown by the analysis is at 

least partly due to the presence of garnet as an impurity in the mineral, it will be interesting to determine the effect producible by 

ammonium chloride upon that species.

In Schneider and Clarke's investigation, conducted in open crucibles, this same leuchtenbergite, after three heatings with ammonium 

chloride, gave up 3.98 per cent of magnesia upon leaching with water. 

The residue contained a little magnesium Oxychloride. With clinochlore from Slatoust similar results Were obtained. A double heating 

with ammonium chloride extracted 2.12 per cent of magnesia, and a 

triple heating took out 3.80 per cent.

XANTHOPHYLLITE.

Variety waluewite, from the Nikolai-Maximilian mine, district of

Slatoust, Urals. Examined by Schneider and Clarke, who found the 

mineral to be practically unattacked by gaseous hydrochloric acid, 

but completely decomposable by the aqueous acid. A triple treating 

with ammonium chloride in an open crucible took out 0.48 per cent of 

lime and 0.61 of magnesia. This amount of decomposition is insignificant.

THE ACTION OF AMMONIUM CHLORIDE ON EOCKS.

From the evidence so far presented it is clear that the ammoniumchloride reaction has much theoretical interest and that it adds a 

good deal to our knowledge of chemical constitution. But does it go 

any further than this and render any assistance in the elucidation of 

other problems? Consider, for instance, the rational analysis of 

silicate rocks that is, the quantitative determination of certain mineral constituents as distinguished from the ordinary estimation of the 

oxides is the reaction of any service here? We have found that 

among the rock-forming minerals analcite and leucite are completely 

transformable into ammonium salts, while elseolite and the feldspars 

are but little affected; olivine and the ferro-magnesian silicates also 

react but slightly. It would seem, therefore, as if analcite and leucite 

might be approximately determined by means of the reaction, the 

amount of change produced in a rock mixture being some measure of 

their quantity. To test this supposition, we have made a number of 

experiments, using for the purpose well-known rocks which had been 

studied both mineralogically and chemically.

Our method of procedure has been extremely simple, and no refinements of process have as yet been attempted. Each rock, in fine 

powder, was mixed with four times its weight of ammonium chloride 

and heated for several hours in a sealed tube to 350°. After cooling, 

the mixture was leached with water, and the amount of alkali passing into solution was estimated. From this soluble alkali the amount 

of analcite or leucite in the rock may be be roughly inferred, but of
54 ACTION OF AMMONIUM CHLOEIDE ON SILICATES. [BULL. 207.

course not with any great degree of accuracy. Still an approximate 

estimation is better than no measurement at all and is of service to 

the petrographer. Fortunately the errors of the process are to someextent compensatory; a little analcite or leucite will always escape 

transformation, while on the other hand a little alkali will always be 

yielded by other species. One error renders the estimation of the 

alkali too low, the other makes it high, but the two tend to balance 

each other. In the ordinary process for separating soluble from 

insoluble silicates by means of aqueous hydrochloric or very dilute 

nitric acid the same errors occur, but with additional complications 

due to the solution of magnesian minerals like olivine. Furthermore, 

aqueous acids will not discriminate between analcite and nepheline, 

two species which behave very differently toward dissociating ammonium chloride. So much premised, we may pass on to the description 

of our experiments.

First, we examined three rocks from the Leucite Hills, Wyoming, 

which were analyzed by Hillebrand and described by Cross/' Their 

mineralogical composition is as follows:

A. Orendite. Contains predominating leucite and sanidine, with phlogopite, a 

little biotite, diopside, and amphibole, and accessory apatite and rutile.

B. Wyomingite. Contains phlogopite, leucite, diopside, and apatite.

C. Madiipite. Contains predominating diopside and phlogopite, with perofskite 

and magnetite, in a glassy base, which has approximately the composition of 

leucite.

On A and B duplicate determinations were made, but only one in 

the case of C. The substances extracted by leaching, after treatment 

with ammonium chloride, are given below:

ALA, Fe20s ----------------

CaO. ........... ............

K20.- -------------------

Najp-.. ....................

Al.

0.26

1.28

4.68

25

A 2.

0.21

1.48

4.53

.43

Bl.

0.64

1.67

9. 50

1.33

B2.

0.64-

1.70

9.38

1.35

C.

0.21

5.00

6.81

1.08

The duplicates are fairly concordant. If now we regard the K2O 

thus extracted as a measure of the leucite in each rock, giving the 

mineral its normal composition KAlSi2O6 , we have the following percentages of the latter: 

In orendite:

1........................................................ 21.81

2_-_--...- --..........---....-...-..-.-.........._____._. 21.11

In wyomingite:

1 ............'.......................,.................... 44.47

2........................................................ 43.71

In madupite ......................................... l ... .... 31.73

"Am. Jour. Sci., 4th series, Vol. IV, p. 115. See iilso Bull. U. S. Geol. Survey No. 168, pp. 85 and 

6,1900, for analyses.
CLARKE AND~1 

STETOEB. J ACTION OF AMMOKITJM CHLORIDE Otf BOCKS.

Two other leucite rocks were also studied by us, as follows, both 

being given in duplicate:

D. Missourite. Highwood Mountains, Montana. Described by Weed and Pirsson.« Analyzed by E. B. Hurlbut. Contains augite and leucite, with apatite, 

iron oxides, oliviiie, and biotite. Some zeolites and analcite are also present.

E. Leucitite, Bearpaw Mountains, Montana. Described by Weed andPirsson. & 

Analyzed by H. N. Stokes. An olivine-free leucite basalt. Contains leucite, 

augite, iron oxides, rarely biotite. and a very small amount of glassy base.

The following substances were taken out by the ammonium chloride reaction:

CaO .................................

K2O... ....... ... ... ................

Na,0..- .............................

Dl.

1.78

4.09

.59

D2.

1.70

3.74

.64

El.

0.89

6.19

1.44

E2.

1.29

6.16

1 47

Hence we have for leucite 

In missourite ...................................... 19.06 and 17.43

In leucitite .......................... r ............. 28.84 and 28.70

It will be observed that the extracted soda is neglected in the computation. In. missourite it may represent analcite; in the other 

rocks it perhaps belongs to a sodium equivalent of leucite, or it may 

come from some still different source. At all events, it serves to indicate some of the uncertainties attending the application of the 

method.

Among the rocks containing analcite as an essential constituent, 

only two were available for our purposes. They are:

F. Analcite-basalt, from Basin, Colorado. Described by Cross. c Analyzed by 

Hillebrand. Contains phenocrysts of augite. olivine, and analcite; also magnetite, and minor amounts of alkali feldspars, biotite, and apatite.

G. Heronite, from Heron Bay. Lake Superior. Described by Coleman.^ Contains analcite, orthoclase, labradorite, aegirite, limonite, and calcite.

By treatment with ammonium chloride the following bases were 

extracted from these rocks, determinations being made in duplicate:

CaO ....... ...........................

K,O... .......................... .....

NajO... ..............................

Pi.

1.74

.46

3.42

P2.

2 28

.49

3.29

'Gl.

1.64

.21

6.04

G2.

1.62

.18

6.37

«Am. Jour. Sci., 4th series, Vol. II, p. 315; Bull. U. S. Geol. Survey No. 168, p. 133. 

6 Am. Jour. Sci., 4th series, Vol. II, p. 143; Bull. U. S. Geol. Survey No. 168, p. 136. 

 - See Bull. U. S. Geol. Survey No. 168, p. 146. 

''Jour. Geology, Vol. VII, p. 431.
56 ACTION OF AMMONIUM CHLOKIDE ON SILICATES. [BULL. 207.

Hence, reckoning the soda as equivalent to normal analcite, 

NaAlSi2 06 .H2 0, \yehave as percentages of the latter-:

In analcite-basalt .................................... 26.33 and 25.33

In heronite ......---..--.---.-----..----.-...--.-... 46.51 and 49.05

According to Coleman's computations, heronite contains 47 per cent 

of analcite. This figure agrees quite perfectly with our experimental 

determination.

In order to gain some notion of the extent to which other rocks, 

containing neither analcite nor leucite, might be affected by the 

reaction with ammonium chloride, four examples were chosen from 

among the many which have been studied in this laboratory/' They 

were:

H. Phonolite, Uvalde County. Tex. Contains sanidine, nepheline, and aegirite, 

with very little brown hornblende, augite, and magnetite.

I. Soda-granite-porphyry, Merced River, Mariposa County, Cal. Contains feldspar, largely albite, hornblende, muscovite, epidote^ apatite, and iron ore:

J. G-ranitite,Placerville Canal, Eldorado Coiinty, Cal. Contains biotite, orthoclase, plagioclase, and quartz.

K. Augite-latite, Table Mountain, Tuolumne County, Cal. Contains labradorite, olivine, atigite, and magnetite.

The bases extracted from these four rocks were as follows, in 

percentages:

ALA,, Fe2Ov---____ ._..--___.--..-----

CaO : -...--- ...............

K20. ..................................

NajO..'... ....- ... ...... .-..........--

, H.

0.33

22

.41

4.38

I.

0.19

29

.20

.33

J.

0. 58

none

.20

23

K.

0. 66

1.21

.66

Among these rocks only the first one, the phonolite, was seriously

affected; and it is difficult to account for the large amount of soda 

extracted. Neither nepheline nor aagirite taken alone gives up nearly 

so much soda as was liberated in this case, and no other sodium mineral has been reported present in the rock. In the other cases the 

amount of extraction is small and amounts to no more than the plus 

error, which was pointed out at the beginning of this discussion.

Taking all things into account, it seems probable that the analytical 

method proposed, although far from exact, is capable of some development, and is likely to yield results of some value. Perhaps it might 

be improved by taking into account the quantities of ammonia retained 

by the washed residues. From that source one estimate could be 

derived, and from the alkali in solution another; the two should give 

better information than either determination alone. But the precision of ordinary analytical processes is not to be expected here, and 

only useful approximations can be anticipated.

« For additional data and the analyses, see Bull. U. S. Geol. Survey No. 168, pp. 62,199, 205, 207.
CLARKEAND"! «TTMMAT?V ' 57 STEIGER. J bUMJMAKY. 01

SUMMARY.

In the foregoing pages we have considered the action of ammonium 

chloride, at its temperature of dissociation, upon 31 mineral species. 

We have shown that its influence upon various silicates differs very 

widely, but that in general it is a much more powerful reagent than has 

been generally supposed. The results, in brief, are as follows:

First. Analcite, leucite, natrolite, and scolecite, heated with dry 

ammonium chloride to 350° in a sealed tube, yield alkaline chlorides 

and an ammonium aluminum silicate, which is stable at 300°. The 

reaction is simply one of double decomposition, the sodium or potassium of the original silicate being completely replaced by ammonium. 

Analcite and leucite give the same product, NH4AlSi2 06 . Natrolite 

and scolecite yield the salt (NH4 ) 2 Al 2Si3 010 . The latter compound is 

a derivative of orthotrisilicic acid, H8Sis010 ; and in a separate section of the memoir its constitution and its relations to other trisilicic

acids are considered.

Second. A similar reaction, a double decomposition, takes place 

incompletely with stilbite, heulandite, chabazite, thomsonite, laumontite, and pollucite. Part of the monoxide base is removed and replaced 

by ammonium, without change of atomic ratios. Cancrinite is also 

vigorously attacked, and partially transformed into a zeolitic body.

Third. Pectolite, wollastonite, apophyllite, datolite, ilvaite, and 

calamine are violently acted upon by ammonium chloride, and their 

molecules seem to be almost completely broken down. The products 

of the reactions are mixtures, and no ammonium silicates are formed.

Fourth. Elreolite, sodalite, riebeckite, olivine, serpentine, phlogopite, prehnite, orthoclase, albite, oligoclase, aegirite, pyrophyllite, 

leuchtenbergite, and xanthophyllite are but slightly attacked by dissociating ammonium chloride.

In the closing section of the work we have shown that the ammonium 

chloride reaction may be applied to an approximate quantitative 

determination of analcite and leucite in rocks, thereby aiding somewhat in the estimation of their mineralogical composition.

O