DEPARTMENT OF THE INTERIOR 

FRANKLIN K. LANE, Secretary 

UNITED STATES GEOLOGICAL SURVEY 

GEORGE OTIS SMITH, Director 

Professional Paper 95 

SHORTER CONTRIBUTIONS TO 

GENERAL GEOLOGY 

1915 

DAVID WHITE, CHIEF GEOLOGIST 

WASHINGTON 

GOVERNMENT PRJ;NTING OFFlCE 

1916 
EVAPORATION OF POTASH BRINES. 

~y w. B. HICKS. 

INTRODU CTION. 

It has long been known that ma~y American brines, including ocean water, contain potas .. 

sium along with much larger quantities of other salts, and during the last few years investigations have shown that brines from several different localities in the United States contain a 

high percentage of potassium. The development of an economic process for the extraction of 

potassium from these brines 1s a problem of great· importance. The most practical methods so 

far proposed depend on evaporation and fractional crystallization. These facts suggest the 

desirability of knowing just what effect evaporation will have on the various constituents of a 

brine. Much is already known about the subject in a general way, and it is possible to predict 

certain qualitative relations concerning such simple salt solutions as those of sodium and. potassium chlorides and also concerning solutions in general whenever the solid phases are known. 

Theoretically a saturated solution of sodium chloride containing a small amount of potassium 

chloride will deposit on evaporation only sodium chloride ruitil the. solution becomes saturated 

with r~spect to both salts; and a saturated solution of potassium chloride containing a small 

amount of sodium chloride willlikewi.se deposit potassium chloride alone until equilibrium is 

reached. At 30° C. the saturated mixture 1 of these two salts contains 11.7 per cent of potassium 

chloride and 19.7 per cent of sodium chloride. On further evaporation at this temperature no 

change takes place in the composition of the solution, both salts being deposited in such quantities that the potassium-sodium ratios in both liquid and solid phases remain constant . . Other 

instances of such simple relations could be given. Usually, however, solutions of two or more 

salts present much more complicated relations. The number of different ions present and the 

possible formation of other compounds, hydrates, and isomorphous mixtures are the chief 

factors influencing the complexity of the system.. Consequently it is difficult to predict what 

changes will result through the evaporation of solutions containing several different ions. 

Furthermore,- experiments with even the simplest systems do not yield the results that might be 

expected from a theoretical consideration. Precipitates often: carry down mechanically or 

otherwise appreciable quantities of other salts, supersaturation may easily occur, and equilibrium is often slow in reaching its final adjustment. These are all factors of practical 

importance .. 

Experimental results relative to the changes which take place during evaporation, particularly with reference to potassium salts, are rather meager. In his evaporation studies on 

sea water Usiglio 2 found that the potassium in solution increased as evaporation proceeded, 

and the results of his experiments indicate in a general way what happens when sea water 

evaporates. However, in those early days the determination· of potassium, and perhaps other 

constituents, was not capable of the refinement exacted in modern times. Usiglio found that 

the saline residue from sea water contained 0.71 per cent of potassium, ~hile according to 

modern analyses 3 the figure is about 1.1 per cent. Accordingly, it is assumed that Usiglio's 

determinations of potassium in the products of eyaporation may have been likewise erroneous. 

Hence, it is not possible to calculate with any degree of assurance the amount of potassium 

which was; lost by deposition from solution during evaporation. However, it appears that in· 

1 Precht and Wittjen, Deutsch. chem. Gesell. Ber., vol. 14, p . 1667, 18Sl. 

2 Annales chim. phys., 3d ser., vol. 27, pp. 92, 172, 1849. 

a Clarke, F. W., The data of geochemistry, 2d ed.: U.S. Geol. Survey Bull. 491, p. 113, 1911. 

65 
66 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1915. 

concentrating the brine from 5 liters to about 100 cubic centimeters approximately 8 per cent 

of the potassium originally present was lost from solution. In the final mother liquor 3.31 per 

cent of the total salts was potassium, a condition which indicates that the potassium had still 

not saturated the solution, as the total salts of several sea water bitterns from the vicinity of 

San Francisco are reported 1 to contain 5 to fo per cent of potassium. 

Chatard 2 evaporated large quantities of the water of Owens Lake, Cal., which, after being 

reduced to the point of crystallization contained about 0.8 per cent of potassium. The ~xperiments were carried out at the normal temperature..in the vicinity of Owens Lake. A series of 

crops of crystals were obtained, each of which contained about 1 per cent of potassium chloride. 

Unfortunately the weights of the salts and the mother liquors in each experiment are not 

reported, and consequently the relations can not be followed in detail. Another important 

factor, the analysis of the final mother liquor, is also lacking. However, it is probable that the 

solution did not become saturated with salts of potassium because each crop of crystals contained approximately the same percentage of this constituent. This conclusion is strengthened 

by similar results of the evaporation studies on the water of Mono Lake, Cal. 2 In the experiments at Mono Lake the final mother liquor was evaporated to dryness and the residue was 

analyzed. The potassium-sodium ratio in this product was 0.27, which is very strong evidence 

that the final mother liquor was not saturated with salts of potassium, experiments recorded 

'elsewhere in the present paper having shown that in solutions very similar to that in Owens 

Lake the potassium-sodium ratio may become as high as 0.59. According to Chatard's results, 

about 15 per cent of the potassium originally present was lost in the evaporation water of Owens 

Lake long before the bittern became saturated with potash salts. 

Ev~poration studies ori artificial potash brines were undertaken by the writer in the hope 

of throwing further light on the conditions governing the deposition of salts from solutions. 

It was planned to begin the investigation with simple salt mixtures and, by gradually including 

other salts, to deal finally with complex brines comparable with those found in nature. Though 

it has been possible to do only a small part of the experimental work contemplated, it seems 

advisable to publish the data thus far obtained, with the hope of supplementing them later. 

In conducting the experiments an attempt was made to reproduce as far as possible commercial conditions. It is not believed that equilibrium reached final adjustment in the solutions, 

and consequently the results can not be considered as solubility determinations. 

METHODS. 

PREPARATION OF SOLUTIONS. 

In the preparation of the solutions pure anhydrous chemicals were used except in the 

experiments with borates, for which borax was employed. The required amount of each salt 

was weighed out and dissolved in a definite volume of water. The composition of the original 

solutions as recorded in the tables was calculated from the data thus obtained. 

METHOD OF EXPERIMENTATION. 

. In the preliminary exp~riments 150 grams of the solution under investigation was evaporated in a small beaker on the steam bath to about one-fourth its original volume and was 

.allmyed to cool at room temperature, which was between 25° and 30° C. The solution was 

:stirred occasionally while cooling, and care was taken to start crystallization in order to prevent 

supersaturation. After the solution had cooled, it was filtered from the crystals by strong 

~uction into a s~all flask, weighed, and analyzed. 

In all other experiments 500 to 1,000 grams of solution was evaporated in beakers at intervals on the steam bath, and the progress of the results of evaporation was watched by removing from time to time the deposited salts and weighing and analyzing the solution. After each 

I Phalen, W. C., The salt industry of the United States: U.S. Geol. Survey Bull.- (in preparation). 

2 Chatard, T. M., Natural soda: U.S. Geol. Survey Bull. 60, pp. 27-101,1888. 
EVAPORATION OF POTASH BRINES. 67 

stage in the evaporation the solution was stirred vigorously for several hours in an electrically 

controlled ~hermostat, which deviated les.s than _0.05° .f~on: 30° C., ~til the solution attained 

the temper~ture of the bath and appeared to be rn equrhbnum otherr rse. It was then allowed 

to settle, and without change of temperature a sample of it was tr ansferred by means of a 

pipette to a flask and weighed. The sample was drawn out thrmigh a filter consisting of a 

piece of cotton held, in a small funnel which was attached to the pi ette by a piece of rubber 

tubing. The pipette had a capacity of 8.606 cubic centimeters at 20° C., and from these data 

the specific gravity of the solution was calculated. The main pdrtion of the solution was 

filtered into a smaller beaker with strong sucti<Im, as in the preliuainJry experiments, care being 

taken to remove as much as possible of the adhering liquid from !the crystals. The filtrate 

was then returned to the steam bath and was further concentrated to about half it"s volume. I - ... It was then cooled in the thermostat, filtered from the crop of crysrals, and otherwise treated 

as described above for the first product of evaporation, the filtrate being returned to the steam 

bath. The concentration was similarly eontinued at intervals until only a small amount of 

liquid remained. In all the experiments the procedure above desctibed was followed in each 

succeeding stage in the Pvaporation. 

METHODS OF ANALYSIS. 

The weighed samples of solution obtained by the concentration JUst described were diluted 

to definite volume, and aliquot portions r epre"enting 3 to 4 grams lof solution were taken for 

analysis. The determinations were made in duplicate, and practically all the figures given 

in the tables (pp. 68, 69, 71) are the average of two closely agreeing results. Common methods of 

analysis were usually employed, but short cuts were taken wherever p

1

ossible, and a brief description of the procedure therefore seems advisable. The sulphate raaicle was precipitated and 

weighed as barium sulphate, and potassium was estimated by the modified chlorplatinate 

method.1 Sodium was determined by weighing the combined bases ks chlorides or as sulphates 

and subtracting the corresponding equivalent of the potassiunt, bbrates when present being 

first removed by repeated evaporation with methyl alcohol and hydrochloric acid. Chlorine 

was determined by titration with N/10 silver nitrate after neutrali ing the solutionwithnitric 

acid. The borate radicle was estimated by titr ation of the boric acid with N/10 sodium hydroxide in the presence of mannite and phenolphFhalein. The carhondte radicle was determined 

by titrating with N/10 hydrochloric acid in the pr. esence of methyl r! range and sub.tracting the 

borate equivalent. . 

The calculations were made with the slide rule, and a few of the results may differ slightly 

from the true amounts. The percentage of the various constituentJ lost during evaporation is 

stated in round numbers with two significant figures, and no correctio~ was made for the amount 

of salts removed with the sample for analysis. 

1 Hicks, W. B., A rapid modified chlorplatinate method for th e est imation of potassium: Jour. Ind. ng. Ch8m., vo!. 5, pp. 650--653, 1913. 
68 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1915. 

EXPERIMENTAL RESULTS. 

PRELIMINARY EXPERIMENTS. 

In the preliminary experiments solutions nearly sat11rated with salts of sodium and containing much smaller amounts of salts of potassium were concentrated on the steam bath to 

about one-sixth their original volume, it being assumed that the resulting solutions would be 

approximately saturated with potash salts. The solutions were cooled at room temperature, 

filtered, and analyzed. The results are · given in the following table, together with the composition of the original solution and other data: 

Changes re-sulting from the evaporation of artificial potash brines containing one acid radicle. 

Solution before Solution after evaporation. KjN a ratios. evaporation. ....., . 

~ <l) 

C) 

Quantity. Potassium. 1-< ,-.... ,-.... <l) d ,-.... rn ~ d d 8 .s Ill 

~ · 0 0 

Character of solution. ~ ,--... <l) 

....., ..... ..... Ill ....., ell ~ 

1 C) 1-< ....., ::s ~ Ill ell 

~ 1-< ..s 0 1-< <l) '0 §" 0 

s 8 s §" Ill 

:>. ~ ~ ?- "' ~ 

~ .s ~ s ~ .s <l) ?- <l) 

..... rzi <l) rzi <l) <l) ~ 

~ Ill <l) Ill ell 

§ ~ · C) ::s C) s ~ 1-< 1-< 1-< ..... ""' ' :B 1-< ell .2 <l) ::s "' ....., ....., ::s 0 &; <l) • <l) 1-< 0 <l) ....., ~ 

0 0 0 ~ ell Ct r:/1 P-i P-i r:/1 P-i P-i P=l r:/1 

----- - ------------------ KC1+NaCL _____ : . .. __ _ . . _. _ . . _ 150 5.901 1.573 24.1 16 8.50 4.58 1.104 30 0.27 0.54 ao. 79 

C0 +Na C0 ~ •••••• - .-- •• --- 15fr 4. 882 1 1. 698 21.3 14 9.36 6.22 1. 326 22 . 35 . 67 --- --- K2S04+N2S04 ••••• - •• • -.-- .••• 25 .737 .225 6.3 25 4.72 2.72 .170 24 . 31 . 58 .. ., ___ ... 

I 

a Precht and Wittjen, Deutsch. chem. Gesell. Ber., vol. 14, p. 1667, 1881. 

According to these results, the potassiun1 appears to have concentrated most rapidly in 

the carbonate and least rapidly in the sulphate solution, and the potassium-sodium ratio after 

evaporation is greatest in the carbonate solution. It is apparent from the column of ratios 

that the chloride solution had not become saturated with potassium, and it is probable that the 

other concentrated brines had not reached equilibrium. The loss of 20 to 30 per cent of the 

potassium during evaporation shows that a large part of 1;he potassium is removed from such 

brines before the solution becomes saturated with this constituent. · 

ALKALI BRINES CONTAINING. TWO ACID RADICLES. 

In the evaporation experiments with brine3 containing two acid radicles the origin_al 

solutions were ·approximately of the same strength and contained three to four times as much 

sodium as potassium. In each series of experiments 500 grams of the solution was evaporated 

in stages, and the effect of each partial concentration was determined by analyzing the solution 

according to the methods already described. The character of the brines, their original composition, and the results of evaporation are given in the accompanying table. The changes 

in the concentration and the percentage loss of potassium as evaporation proceeded are also 

shown graphically in figures 24 and 25 (p. 70). 
EVAPORATION OF POTASH BRINES. 69 

Changes resulting from the evaporation of artificial potash brines containing two acid radicles. 

P. 

cG 

> 

Solution 

after 

evaporation. 

Percentage composition of the 

solution. Percentage loss. 

Character of solution. ~-@ .s ~ 1----,------1 

I o 1---~~7·~--~--.----1--~~~-~---1~ 

i£ ~ Per ~D Grams. cent. w. 

K. Na. · Cl. Total 

f!alts. K. cG 

N a. Cl. C03 • Z 

~ ----;------1---------------------------------------------

KC!+Na,CO, ......... {! 

K,SO,+Na,CO, ...... { t 

KCl+NaCl+Na2S04 .. { t 

I 3 

KCJ+NaCI+NaCO, .. { i 

KCJ+NaC!+Na,B,O,. {! 

500 100. 0 . . . . . . 2. 10 6, H4 1. 90 9. 06 2:0. 00 ................... -.. 0. 30 

236 57. 2 1. 35 4. 09 11. ii1 3. 68 15. 05 34. 33 8. 0 22 8. 5 22 . 36 

141 28. 2 1. 36 5. 67 10. 97 5. 14 14. 44 36. 22 24 55 24 55 . 52 

49 9. 8 1. 36 7. 48 10. 03 6. 71 13 .. 28 3.7. 50 65 86 65 86 . 73 

804 804 

500 100. 0 . . . . . . 1. 80 6. H4 2. 20 9. 06 2:0. 00 . . . . . • . . . . . . . . . . . . . . . . . 26 

192 38. 4 1. 39 3. 06 13. 00 3. 12 17. 33 3.6. 51 35 28 46 27 . 24 

58 11.6 1.38 ~68 1aso 2. 56 17. 17 3.5: 71 76 79 87 78 . 30 

500 100. 0 . . . . . . 2. 10 

249 49. 8 1. 24 3. 99 

128 25. 6 1. 25 5. 55 

41 8. 2 1. 26 6. 24 

Cl 

6. 87 11.61 

9.16 16.16 

8. 54 16.72 

8. 22 17:.18 

500 100. 0 . . . . . . 2. 10 8. 03 11. 61 

277 55.4 1. 26 3. 55 J.O. 06 14. 72 

117 23.4 1. 29 5. 51 9. 77 14. 02 

60 12. 0 . . . . . . 5. 39 10. fiO 12. 30 

40 8. 0 . . . . . . 5. 10 11. ].2 11. 22 

500 100.0 

166 33.2 

95 19.0 

38 7. 6 

2.10 

5. 14 

6.21 

6. 11 

('!) 11. 61 

8. 38 17. 29 

8. 00 17.41 

8. 15 17. 10 

a A= original solution. 

804 Cl 804 

1. 19 2:1. 77 . . . . . . . . . . . . . . . . . . . . . . . 31 

2. 26 3.1. 57 5. 3 34 27 5. 4 . 44 

1. 96 32. 77 32 68 63 58 . 65 

1.56 33.20 76 9~ 88 89 .76 

co3 co3 

2. 26 24. 00 . . . . . . -. . . . . . . . . . . . . . . . 26 

3. 43 31. 76 6. 4 31 30 16 . 35 

5. 18 34. 48 39 72 72 46 . 56 

7.47 35.66 69 84 87 60 .51 

8. 98 36. 42 81 89 92 68 . 46 

B40 7 B407 

(?) . -.................... - ......... . 

1. 08 31. 89 19 (?) 51 (?) . 61 

1. 60 33. 22 44 . -. . 71 -. . . . . . 78 

2. 28 33. 64 78. . . . . 89 .... -. . 75 

The highest concentration of potassium, 7.48 per cent, was obtained with the solution 

containing potassium chloride and sodium carbonate and the lowest, 3.68 per cent, with that 

containing potassium sulphate and sodium· carbonate. In the chloride-sulphate and chlorideborate brines the concentration of potassium increased to a little :more than 6 per cent, but in 

the solution containing potassium chloride, sodium. chloride, and sodium carbonate it increased 

to a maximum and then decreased. In general the contents of sulphate and sodium varied 

comparatively little after the 'first concentration. The chlorine concentration usually increased 

as evaporation progressed, but in the solution containing potassium chloride, sodium chloride, 

and sodium carbonate it decreased after the first concentration. In that solution the content 

of carbonate continually increased, but in the other carbonate brines it rapidly rose to a maximum and then slowly declined. I The final mother liquor always contained a large amount of 

carbonate.. The borate concentration steadily increased. The amount of dissolved salts 

increased in all the solutions to more than 33 per cent. The two solutions containing both 

ahloride and carbonate yielded the strongest bitt'erns. The variations in the potassium-sodium 

ratio correspond closely to the changes in the concentration of the potassium. The highest 

ratio was reached in the chloride-borate soluti(m, and the lowest in the sulphate-carbonate 

solution. The loss of potassium during the first concentrations was greatest in the sulphatecarbonate solution. The loss of potassium during the first concentrations was greatest in the 

sulphate-carbonate brine. In all the other solutions the loss was only 5 to 8 per cent while the 

solution was being concentrated to about half its original volume and the content of potassium 

was being doubled. During further evaporation the loss was very rapid in all the solutions. 

The steady increase in the percentage of total salts and the continual variations in the concentration of the constituents prove that equilibrium in the solutions did not reach final adjustment. 
70 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1915. 

The variations in concentration of the potassium in the several solutions as evaporation 

proceeded are shown graphically in figure 24. The curve representing the solution containing 

8 .-----.---~------~--~----. 

§6t----t----'--+-----+---+:¥+1-..r-----l 

-;; 

::J 

0 

Ul 

s 

s~o o---~4o_o _____ 3~o-o----z~oo------,o~o-----~o 

Grams of solution 

FIGURE 24.-Diagram showing the rate of concentration of potassium 

in various brines during evaporation. 

potassium sulphate and sodium carbonate is 

practically a straight line whose moderate slope 

indicates that the concentration of the potassium is slow and the loss of it necessarily large. 

The curves representing the concentration of 

potassium in the other solutions are similar to 

one another up to a concentration of about 5.5 

per cent; beyond that point the curve for the 

solution of potassium chloride, sodium chloride, 

and sodium carbonate declines immediately 

and that of the borate reaches a maximuru at 

6.21 per cent. 

Figure 25 gives ta better idea of the losses 

of potassium sustained by the solutions than 

the table. From this it appears that at any 

particular stage in the evaporation the loss 

was least in the solution containing potassium 

chloride and sodium carbonate and greatest 

90r---.----.---~----r---~ 

80~----~----~------+------+---r~ 

in that containing potassium sulphate and sodium 

carbonate. With the exception .of the curve for 

the latter solution the curves are all very much ~ 60 

alike, sloping gently to a point corresponding to ~ 

about half the quantity of the original solution ·~ 

and then becoming very steep. In other words, ~ 5

·

0 

0 

the loss of potassium sustained by the solutions ~ 

during reduction to half their original volume and 

during concentration of the potassium to about 4 

per cent is 5 to 8 per cent of that originally present, 

but during further evaporation the loss is very 

rapid. 

ALKALI BRINES CONTAINING THREE ACID 

RADICLES. 

More extensive evaporation experiments 

were carried out with solutions of the alkalies 

containing sulphate or borate in addition to 

chloride and carbonate. The character and 

composition of the brines used and the changes 

Q) 

E4o~----~----~------+-~--~~--~ 

c 

e 

Q) 

~ 

resulting through evaporation are given in the --!!!!iiiiliiiii~=====:._...l. ---::+-:---:--:,-=-oo=----:o 

accompanying table. The change in concentra- , Gr;3ms of solution 

tion and the percentage loss of potassium for the FIGURE 25.-Diagram showipg the loss of potassium in various 

sulphate solution is plotted in fig. 26 (p. 72). brines during evaporation. 

The corresponding curves for the borate solution are so nearly identical with those given 

that they would unnecessarily confuse the diagram. 
EVAPORATION OF POTASH BRINES. 71 

Changes resulting from the evaporation of art'ificial potash brines containing three acid radicles. 

0 I ~ Percentage loss. 0 Percentage composition of the solution. §' P< """ 0 ~ . """,--.._ ?- >----- """ <D <D 00 >. I ~ 

<D t::l, ~ ~ """ ~<D •.-I ·-< \.) 

Character of the ...c:~ <D ~ ?- ~ -..:>0 """bll ~ CD 0 solution. :;3 ~'-' t'.o Total ~ ~ SP< -~ ~ § K. Na . 01. CO a. 804. .8 ';; K. Na. Cl. C03 • 804. ....... ~ \.) salts. 0·,...., ~ 

00 ,_,_,.;> ~ oo""" ~ <D 

tl() ..8~ 

"""~ \.) 

<D _s~ . z ~ P< 0 

w. """ w. 

0 w. ~ ~ 

------------------- - - -----

A 1, 000 1. 223 2.10 9.18 11.60 2.26 2.39 27.53 7.63 ---- ......... ---- ....... ......... 0.23 

1 723 1. 268 2.86 10.64 13. 53 2.68 3.05 32.76 8.73 1.6 16 16 14 7.5 . 27 

2 547 1. 278 3.67 10.40 13. 5i 3.16 2.96 33. 70 10.89 4.4 38 36 24 32 .35 

KCI+NaCl+ 3 337 1. 285 4.88 9.82 13. 71 3.63 2.30 34.34 14.20 22 64 60 46 67 . 50 

4 213 1. 295 5. 75 9.79 13.39 4. 79 1. 79 35.51 16.19 42 77 75 55 84 . 59 N~C0 +Na 804 .. 5 148 1. 300 5. 70 9.93 . 2@ 5.08 1. 67 35.58 16.02 60 84 83 67 90 . 57 

6 99 l. 314 5.53 10.33 12. 18 6.51 1. 55 36.10 15.31 74 89 89 71 93 .54 

7 55 1. 327 5.34 11.01 11.24 7.84 1. 56 36.99 14.44 86 93 95 81 96 .49 

8 22 1. 335 5.28 11.26 lp 1 8.36 1. 59 37.35 14.14 94 97 98 92 98 . 47 

-- -- B407 B407 

·A 1,000 1. 238 2.10 (?) 11.6 2.27 (?) .......... .. ............ ......... .. ...... ........ ---- 1 653 1. 260 3.13 10.18 14:.3'(' 3.05 1. 46 32.19 9.72 2.6 19 12 .31 

2 541 1. 270 3.57 10.25 14. 10 3.57 1. 70 33.19 10. 76 8 ........ 34 15 ..... .35 

KCI+NaCI+ 3 355 1. 284 4.65 9.86 3.8~ 3.88 2.18 34.37 13.53 23 ........ 58 39 .......... .47 

4 248 1. 310 5. 60 9.74 13.2 4.67 3.01 36.25 15.45 34 ........ 72 49 .. ........ . 57 N~C0 +N~ . 5 165 1. 339 5.26 10.53 11.8* 6.23 4.13 37.97 13.85 59 ........ 83 55 --·-- .50 

6 104 l. 368 5.11 11.10 l 0. 9Q 7.02 5.45 39.58 12.91 75 ---- 90 68 ..... .46 

7 49 1. 378 5.03 11.45 9. 46 8. 77 6.29 41.00 12.27 88 ---- 96 81 ............ .44 

8 17 1. 388 4.82 11.80 9. 42 8.63 6.39 41.06 11.74 96 .......... 98 93 ..... , . 41 

a A= original solution. 

As evaporation progressed the potassiUin concentration of both solutions increased to 

about 6 per cent and then gradually decreased. The chlorine concentration rose to a maximum in each solution and then decreased. The c, rbonate con'centrates increased ra p idl y in both 

brines, but finally showed a slight decrease in t'fu.e borate solution. The borate concentration 

rose steadily to 6.39 per cent. The changes in 1

he percentages of sulphate and sodium were 

slight. The quantity of dissolved salts in both 1

solutions became greater as evaporation progressed. The final sulphate mother liquor con ·ained 37.35 per cent of salts and that of the 

borate 41.06 per cent. J 

In the sulphate solution the potassium-sod.i~m ratio increased from 0.23 to 0.59 and then 

decreased to 0.47. In the borate solution it reached a maximum of 0.57 and then decreased 

to 0.41. I 

The percentage of potassium lost from o~h solutions increased slowly until the brines 

had been reduced to about half their original vo~ume. At this point the concentration of the 

potassium was about 4 per cent, and the loss amounted to 5 or 6 per cent of the potassium 

·originally present. On further evaporation the jloss was very rapid. At the maximum concentration of potassium only about one-fifth of the solution remained, and a loss of more than 

.35 per cent is recorded. By means of. the curves\ in figure 26 the percentage loss corresponding 

to any concentration of potassium can be direetly determined. . I 

CONCL~SION. . 

According to the results set forth in this paper, the potassium is concentrated best in brmes 

-containing carbonates and chlorides, and poorest\ in those containing sulphates and carbonates, 

though a small amount of sulphate does not seef to hinder the concentration materially. In 

brines that contain several acid radicles the cope ntration of potassium n1ay increase to a maximum as evaporation proceeds and then decline. The evidence at hand indicates that a large 

:percentage of the potassium in a solution is lost Uuring evaporation before the maximum con-
72 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1915. 

centration of potassium is .attained. The loss is small until the potassium reaches a concentration of about 4 per cent, but it is very rapid during further evaporation. Therefore in the 

commercial extraction of potash from brines, especially those of the alkalies, it would seem 

c 

0 

6 

5 

S4 

0 

rJ) 

£ 

E 

.2 3 ~ ro 

0 

0. 

l.t-

~2 "O.D 

ro 

c 

Q) 

() 

~ 1 (l_ 

I 

~ \ 

~ ~ 

~ ------

--__/ 

/ 

-. I 

v 

I / v ~ ~ 

v 17 

, j \ 

.:, 

7 

I 

~ 0 

~ r 0 

« 

v 

0 

ljOOO 900 800 700 600 500 400 300 200 100 

Grams of solution 

100 

~0 

80 

70 

~ 60 ~ 

·u; 

l? 

~ 0 

0. 

50t Q) 

'00 

ro 

c 

40 ~ 

30 

20 

10 

0 

0 

I.. 

Q) 

a.. 

FIGURE 26.-Diagram showing the rate of concentration and the loss of potassium during the evaporation of a brine containing 

chlorides, carbonates, and sulphates of the alkalies. 

best first to concentrate the solution by evaporation until it contained about 4 per cent of potassium, and then to subject the resulting bittern to other processes of manufacture. J-'he most 

advantageous point of concentration would, however, have to be determined for each particular 

brine.