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 
AN ANCIENT VOLCANIC ERUPTION IN THE UPPER YUKON BASIN. 

By STEPHEN R. CAPPS. 

It has long been known that a large area in Alaska and Yukon Territory is covered by a 

layer of volcanic ash. The ash lies near the surface, beneath a thin covering of soil or silt, 

and gives evidence of an explosive volcanic eruption that in terms of geologic history is very 

recent, though antedating historic record in this part of the world. The first published description of this material is that given by Schwatka,t who observed the ash layer along the banks 

of Lewes River and its headward tributaries in 1883. In 1887 Dawson 2 extended the known 

area of the ash and estimated its total area, the direction from which it came, and the approximate length of time since it was deposited. In 1891 Hayes, 3 in company with Schwatka, 

conducted an exploration from Fort Selkirk, on the Yukon, to the Copper River basin. They 

traveled westward into an area in which the ash gradually increased in thickness to its maximum 

near the international boundary and rapidly-thinned west of that line. In 1898 and 1899 

Brooks 4 explored the headwaters . of White and Tanana basins and made n1any observations on the areal distribution and thickness of the ash. The present article is based largely 

upon information personally obtained or collected by Mr. Brooks. The writer first became 

interested in this occurrence in 1908, when working in the N abesna and White River district,5 

and a second expedition into the same general region in 1914 gave opportunity for a more 

extended study of the ash fall. Records of the outer limits of the ash-covered area have been 

taken from many sources, especially from the published and unpublished notes of the members 

of the Geological Survey of Canada and of the United States Geological Survey. 

The general outlines of the ash fall are shown on figure 23, the relative thickness of the 

deposit being indicated by contours. The outer limits of the area are drawn to include all 

points at which the ash has been observed and at which it is still recognizable as a distinct 

layer. Without question a thin film of dust could at the time of the eruption have been 

observed over an enormously greater area than that here outlined, but, as will be shown, the 

ejection of the ash antedates recorded history in America, and the area affected can now be 

determined only by the presence of the ash that has been preserved. Less than one-fourth 

inch of ash falling at the time of this eruption over a vegetation-covered upland would probably 

be insufficient to form a layer that would now be generally recognizable. 

The outermost observations recorded include, on the west, observations on N abesna, 

Tanana, and Yukon rivers, by Brooks and others; on the northeast and east, on Gravel, 

Macmillan, and Pelly rivers, by Keele, .Dawson, and McConnell; on the southeast, on Teslin 

River and at Lakes Marsh and Bennett, by Schwatka, Dawson, and others; and on the south 

and southwest, along the southeast flank of the St. Elias Range, by Hayes, Brooks, and the 

writer. . 

The ash usually appears along the cut banks of the rivers as a thin white band near the 

top of the bank, covered by only a few inches or a foot or two of soil, silt, or vegetable humus. 

It is remarkably persistent and is in places continuously exposed for miles. Over any given 

1 Schwatka, Frer!erick, Along Alaska's great river, Cassell & Co., New York, 1885. 

2Dawson, G. M., Report on an exploration in the Yukon District, Northwest Territory, and adjacent northern portion of British Columbia: 

Canada Geol. and Nat. Hist. Survey Ann. Rept., vol. 3, pt. 1, pp. 43 B-46 B, 1889. 

3Hayes, C. W., An expedition through the Yukon district: Nat. Geog. Mag., vol. 4, pp. 146-150, 1892. 

4Brooks, A. H., A reconnaissance in the White and Tanana river basins, Alaska, in 1898: U.S. Geol. Survey Twentieth Ann. Rept., pt. 7, 

p. 475, 1900. 

o Moffit, F. H., and Knopf, Adolph, Mineral resources of the Nabesna-White River district, Alaska, with a section on the Quaternary by S. R. 

Capps: U. S. Geol. Survey Bull. 417, pp. 42-44, 1900. 

59 
60 · SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1915. 

district of small area ~he ash tends to be rather uniform in thickness, although locally it thickens 

into lenses or thins out entirely. It occurs prevailingly in a single layer, was apparently ejected 

during one period of eruption, and fell as one continuous shower in which there were no time 

breaks of sufficient length to interrupt the vertical continuity of the deposit. At a few localities two or nwre ash beds, one above the other, separated by beds of soil or silt, have been 

observed, but the sporadic nature of these occurrences and the great preponderance of areas 

with but a single layer indicate that where two or more superposed layers occur the upper layers 

are composed of ash derived by erosion from the lowest one and deposited later by wind or 

by streams. The evidence, therefore, is strongly in favor of but a single period of eruption. 

The ash bears a close relation to the present topography, occurring not only over the 

valley :floors of the present stream basins but also over the intervening hills and ridges. Shallow 

excavations on hillsides and in valleys everywhere reveal its presence~ Burrowing animals, 

s

8

oc::EI::E3:o===::::5:E0==:=3100 :Miles 

LOCALITIES AT WHICH 

ASH HAS BEEN OBSERVED 

No. I thickness I inch 

" 2 1.5 inches " 3 1.5 

" 4 5 

" 5 5 

" 6 8-12" 

" 7 .75 " 

" 8 1-1.5 " " 9 3-5 " 11 IQ 4-6 II 

" II 2 

" 12 3 

" 13 6-12 " 

" 14 2-3 " " 15 1.5 feet 

" 16 2 inches " 17 300 feet II 18 50-75 II 

,, 19 3-5 " 

" 20 2 

"21 1.5 " 

" 22 3 inches· 

" 23 I inch 

x = Ash now present, but 

thickness not observed 

FIGURE 23.-Map of upper Yukon basin, Alaska and Yukon Territory, showing distribution of volcanic ash. 

especially the spermophiles, or striped gophers, avail themselves of the ease with which the ash 

can be excavated, and their mounds are in many places composed almost entirely of this material. 

Furthermore, the low terraces of streams, covered with an ash layer, show that the material fell 

at a very late stage in the development of the present stream gravels. The ash overlies all but 

the most recent stream deposits and is much younger than the glacial materials deposited during 

the last great period of glaciation. 

The thickness of the ash increases gradually, but by no means symmetrically, from the 

edges toward the center of the area covered. The great· highway through this part of Yukon 

Territory and Alaska by way of the White Pass & Yukon route to the navigable waters of 

the Yukon basin follows directly across the ash-covered area, from southeast to northwest. 

Along this route the ash is particularly well exposed in the river banks. It first appears near 

Lake Bennett as a layer an inch or less in thickness, but increases to a maximum of about 1 
U. S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 95 PLATE VI 

A. AN ASH-COVERED LANDSCAPE, UPPER KLETSAN CREEK, NORTHERN FOOTHILLS OF 

MOUNT NATAZHAT, ALASKA. 

White deposit is ash except on high summits, whi ch are covered with snow. Photograph by United States 

Coast and Geodetic Survey. 

B. ASH DRIFT ON NORTHERN FOOTHILLS OF ST. ELIAS RANGE, ALASKA, NEAR 

INTERNATIONAL BOUNDARY. 

Snow on high summits. 

G. PEAT BLUFF, WITH VOLCANIC ASH LAYER, ON WHITE RIVER, ALASKA. 

Overturned peat blocks in foreground. 

. I 

AN ANCIENT VOLCANIC ERUPTION I N THE u;PER YUKON BASIN. 61 

foot toward the northwest in a portion of the Teslin and Lewes river basins. Below Fort · 

Se~kirk it thins gradually northwes.tward, and beyond Eagle i~1 is only an inch or less in thickness . 

Dawson 1 early recognized that the ash thickens from the Pelly westward toward the Lewes 

and must have come from the west. He suggests that it ma1 have been derived from a volcano 

of the Mount Wrangell group. Hayes/ however, who cross~d from Fort Selkirk to the head of I 

White River in 1891, observed the increasing thickness of the ash to an area between Klutlan 

Glacier and Kletsan Creek, on the north flank of the St. EThas Range, and a rapid decrease in 

thickness west of that area. Brooks 3 'confirmed Hayes's dbservations in 1899. It was thus 

proved definitely that the material .was not derived .fro. m thE volcan. o.es of the Mount Wrangell 

group, but from some source much farther east. By a plol.lJting of the observations obtained 

from all sources the data shown on figure 23 as to distrib~Eon and thickness of the as.h were 

obtained. Within the area outlined by the 3--foot COfl:tOI the ash occurs locally in great 

thickness. Hayes noted beds between 75 and 100 feet thick on the western bank of the Klutlan, 

where there is. no reason to suppose that the original thicknes~ had been increased at the expense 

of surrounding ~egions, except, perhaps, by wind drift. Near the head of Kletsan Creek, 9n 

both si~es of the international boundary, there is an area 2 o 4 miles wide, along the mountain 

flank, in which the entire surface is covered with great white t anks and dunes of ash (Pl. VI, A). 

The area is for the most part above timber line, vegetation on its surface is sparse or lacking, 

and from a little distance one receives the impression that he is looking over great banks of snow 

(Pl. VI, B). The surface of this area is dotted with lakelets the ash shifts with the winds, and 

the hills are modified dunes. The presence of ground frost ell se to the surfat?e, however, retards 

to some extent the movement of the ash by winds. The be t of ~hick ash has a relief of 200 to 

400 feet, which is believed to be largely in the ash, as exppsures of the underlying rocks are 

almost completely lacking. ~ 

It is quite evident from the great thickness of the ash alpng the south flank of the St. Elias 

Mountains near the international boundary that the vent om which it was ejected is in that 

neighborhood. Thomas Riggs, jr., while engaged in survey-4lg the international boundary line~ 

noticed a small crater in a glacial 'cirque 4 miles north-northe~st of Mount N atazhat, from which 

he thinks ·it probable that the ash was ejected. The writer, in 1914, attempted to visit this 

crater, but a heavy snowfall early in July and a shortage of I provisions prevented waiting until 

the snow should melt sufficiently to allow an inspection of the reported crater. All the evidence 

so far obtained, however, both as to the areal distribution lof the ash and as to its thickness, 

points to some crater near the northern border of the St. Elits Mountains near the international 

boundary as the vent from which the ash came, and it is nl t improbable that the locality sug- . 

gested by Riggs is the true one. · 

The distribution of the ash from its center of dispersion ndicates that the winds at the time 

of the eruption blew from the west and south. The long ea t-west axis of the ash-covered area 

and particularly that of the area of ash 1 foot or more thi.ct shows that the wind at ·the time 

. of the greatest ash fall blew almost directly from west to eatst. The great breadth of the area 

in the north-south ~irection near its western margj~ also po nts to a shifting of t~e wind to the 

south, probably dur1ng the later stages of the eruptwn, for lthough ash was carried northward 

a distance of 300 miles from the crater, the 1-foot contour tends northward less than 50 miles 

from the center, whereas it reaches eastward a distance ~ at least 220 miles. The greatest 

distance from the center at which the ash layer has been r, cognized is on the eastern slope of 

the Mackenzie-Yukon Divide, in the basin of Gravel River, "1here J. Keele 4 reports it, 450 miles 

from the center of dispersi~n. The southern limits of the h area in the vicinity of the crater 

are not known, for they lie in an unexplored and almost inaccessible field of glaciers and rugged 

mountains. In figure 23, therefore, the southern margin islextended little beyond the area of 

thickest ash, though the ash may have fallen considerably £arther south. 

Estimates of the area covered by this ash deposit have Been made from time to time, based 

on the facts as to distribution then ·available. The first of thkse estimates was nuide by Dawson, 

1 Op. cit., p. 44 B. 2 Op. cit., p. 148. a Brooks, A. H., unpublish d notes. 4 Letter to A. H. Brooks. 

82646°-16-5 
62 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1915. 

in 1887. Although stating that the total area must necessarily be ;much greater than the area 

of his observations, he estimated a ;minimum area of 25,000 square miles covered by ash. Hayes, 

in 1891, with additional information at his disposal, increased the estimate to 52,280 square 

miles. Brooks, in 1906, after having extended the known distribution westward to longitude 

143° W. and northward to the Yukon below Eagle, placed his estimate at about 90,000 square 

miles. By using some additional data, in particular Keele's observation of the ash in the basin 

of Gravel River, the writer has mapped (fig: 23) an area of 140,000 square miles covered by a 

layer of ash. It is well known that in volcanic eruptions of this kind, with extensive ejections 

of pumice, the dust remains in the air for a long time, and a film of ash, too thin to be observable 

after the lapse of centuries, is deposited over large areas of the earth's surface. No doubt 

if the facts were known, the area over which a visible layer of volcanic dust was deposited after 

this eruption would be measured as several hundred thousand or perhaps several millions of 

square miles. 

Two estimates of the volume of ash ejected have been published. Dawson, assuming an 

area of 25,000 square miles and an average depth of ash of 3 inches, estimated that the ash 

would form a prism. 1 mile square and 6,240 feet high. Hayes, taking an area of 52,280 square 

;miles, assu;m.ed that the ash had the shape of a flat cone of that base, and an apex 5d feet in 

height. His estimate gave a volume of 165 cubic miles, over 138 times the figure reached by 

Dawson. It is obvious that this estimate is not based on defensible grounds, for the ash is not 

in the form of a cone, but if deposited on a level area its surface slopes would be decidedly concave. The distance from the head of Kletsan Creek north to White River is only about 12 

miles, yet in that distance the ash decreases in thickness from. 200 feet or more to less than 3 

feet. According to Hayes's. assumption, the ash should be 25 feet thick at distances of 110 to 

185 miles from the center of dispersion. Observations over the area affected are still far too 

few to afford a basis on which accurate estimates of the amount of ash discharged can be made, 

but a provisional estimate, from. the data now at hand, is given here. In making this estimate 

it has been assumed that in the outer zone, beyond the 1-foot ash contour, the ash averages 2 · 

inches in thickness. This assumption seems reasonable, for over a large area of the outer zone 

average thicknesses of 5 to 6 inches have been observed, and even near the outermost margins a 

thickness of 1 to 1! inches is common. Between the 1 and 2 foot contours an average thickness 

of 15 inches is assumed, and between the 2 and 3 foot contours a thickness of 27 inches. The 

average thickness in the inner zone, with 3 feet or more of ash, is placed at 10 feet, although it 

is known that several hundred square miles is covered to depths of 25 to perhaps 300 feet or 

more with ash. The amount of ash derived by a calculation from the above figures gives a total 

volume of about 10 cubic miles. This figure is nearly eight and a half times that obtained by 

Dawson but only 6 per cent of that obtained by Hayes. The true figure is probably considerably ;more than 10 cubic miles, for no account has been taken of the great quantity of 

ash that fell as a thin film of dust far beyond the boundaries here shown. 

The violence of the eruption at the time this ash was ejected may well be inferred by comparison with volcanic eruptions of historic times. Martin 1 has collected statistics on a number 

of such eruptions, and the figures used below are taken from his paper. The most violent 

volcanic eruption of historic record was that of Tomboro, on the island of Sumbawa, east of 

Java, in 1815. Estimates of the volume of ;material ejected reach figures of 26.6 to 50 cubic 

miles, and the area over which the ash fell was probably much greater than during the eruption 

here discussed. Krakatoa, in 1883, is said to have ejected an a;m.ount of ash about equal to 

that thrown out by Kat;m.ai, in June, 1912, or about 5 cubic ;miles. From. the Katmai eruption 

the ash fall was perceptible at a distance of 1,200 to 1,500 miles. ·The greatest distance from 

the probable center of eruption in the White River basin to the margin of the ash fall, as now 

known, is only 450 miles, but it seems probable that if observations had been ;made at the time 

of the eruption, the distance would have been at least equal to that at which the Katmai ash 

was recognized. From the depth of the ash from the White River volcano at its thickest 

1 Martin, G. C., The recent eruption of Katmai Volcano, in Alaska: Nat. Geog. Mag., vol. 24, No.2, 1913. 
AN ANCIENT VOLCANIC ERUPTION IN THE UPPER YUKON BASIN. 63 

development, the· area covered by it, and the enormous volume of. aterial ejected, it is evident 

that the eruption was comparable in magnitude to any that h ve occurred during historic 

times. Unfortunately no facts are available, or are likely .to b , as to the duration of the 

eruption, the violence of the detonations and the accompanying ea thquakes, and the intensity 

and duration of the ash fall, which must have darkened the sun fo days. 

The physical and petrographic character of the ash at a numbe of places has been described 

by others, and no special study has been made by the writer. As was to be expected, the ash 

or pumice is coarsest near the center of eruption and becomes prog essively finer as the distance 

from the center increases. :Within the area of thickest ash the pa ticles average perhaps from 

1 to 3 millimeters in diameter, though larger pieces are numerous, nd single fragments 8 or 10 

centimeters in longest diameter were seen. Near the outer limits of the ash-covered ·area the 

material consists only of very fine dust. A san1ple collected by J. Keele from the basin of 

Gravel River, about 420 miles from the center of eruption, was s bjected to a screening test 

and also measured under the microscope. The ordinary wire scr ens of 60, 80, 100, and 200 

meshes to the inch were used, and the results are shown below, hese sizes being reduced to 

millimeters: 

Caught on 0.423-millimeter screen ............ ___ _____ ____ __ __________________ . __ per cent.. 7. 72 

Caught on 0.317-millimeter screen._ ... __ : .. _. __ . ___ .. _. _______________________ -_-_.- .. do.... 2. 46 

Caught on 0.254-millimeter screen. _______________ __ _____ _______________ ---_-_----- .do.... 4. 78 

Caught on 0.127-millimeter screen._. ______ __ ____ ___ __ _______ ______________ ---_--.-- .do .... 11.28 

Passed through 0.127-millimeter screen._ .. _. ____ . __ . . ____________ . ______ __ _____ .. _ .. do .... 72.94 

The material caught on the two coarsest screens contained a 1 rge proportion of vegetable 

matter and sand particles. As examined microscopically the large t particle of ash seen had a 

diameter of 0.25 millimeter; the smallest 0.002 1nillimeter; the size appeared to be 

about 0.01 millimeter. 

Dawson describes the ash from the Pelly and Lewes basins as 

a fine white sandy material, with a harsh feeling when rubbed between the fing rs. Microscopically it is found to 

consist chiefly of volcanic glass, part being merely frothy and pumaceous, but of hich the greater portion has been 

drawn out into elongated shreds, frequently resembling the substance known as Pe e's hair, and in which the inclosed 

vesicles become more or less completely tubular. In addition to this glass, frag ents and small perfect crystals o~ 

sanadine feldspar occur, together with portions of minute crystals of hornblende a d probably other minerals. 

Knopf/ who studied the coarser material from the White Riv r basin in Alaska, gives the 

following description: 

The "ash" is a white frothy glass, light enough to float on water. The larg r fragments of the pumice inclose 

numerous small hexagonal plates of biotite, short prisms of hornblende a millime er in length, and less conspicuous 

crystals of glassy feldspar. In thin section the hornblendes, which are deeply leochroic in tones of brown, show 

ideally perfect cross sections and terminated prisms; the biotites are also finely d veloped and hold some inclusions 

of apatite. The feldspars are less perfectly crystallized. Both unstriated and lam Hated varieties are present, but all 

possess indices notably higher than balsam. Zonal banding is not uncommon. Optical tests on striated Carlsbad 

twins prove that the feldspars belong to a species somewhat more calcic than 1An1• They inclose some minute 

foils of biotite. Grains of magnetite occur sporadically. The matrix holding thes phenocrysts is a pumaceous glass, 

clear and colorless, with a marked drawn-out, twisted, and fluidal appearance. orne of the phenocrysts show that 

they were broken by the movements of the surrounding glass. According to the jcroscopical determination the ash 

is an andesitic pumice. 

So far as is known, the ejection of the ash was unaccompan"ed by the outflow of lavas. 

No volcanic bombs or pyroclastic materials other than the ash have 1 een noted, and it is probable 

that the outburst consisted solely of violent explosions which carrie the ash outward but failed 

to yield other . types of volcanic material. 

All who have writte~ of the volcanic ash in this district have recognized the fact that the 

eruption must have happened no great number of centuries ago. awson observed that as the 

rivers havenot cut their beds perceptibly deeper since the deposit as laid down on their flood 

plains, the period to which the ash belongs c~;tn not be exceedingly emote. He also noted that 

at one place on the Lewes the ash rests upon a layer of stratified s nds a few feet thick, and the 

1 Moffit, F. H., and Knopf, Adolph, op. cit., pp. 43-44. 
64 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1915. 

sands overlie a mass of drift logs stj)l quite sound and undecayed. From these and other 

facts Dawson believes that the date of the eruption, though at least several hundred years ago, 

can scarcely be more than a thousand years ago. Hayes arrives at a similar conclusion, but from 

different facts. He believes that the freedom of large ash areas from tundra moss1 which 

covers with great readiness even the most barren surfaces, indicates the youth of the ash. 

He states that although great quantities of ash must have fallen on the surface of Klutlan 

Glacier and its neve fields, the fact that nearly all the ash now found there is in the terminal 

moraines, that on the stagnant ice extendip.g only a short distance back from its front, i:Q.dicates 

that since the eruption the ice which then formed the neve has moved the entire length of the 

glacier and deposited its ash in the terminal moraine. This he thinks must have required 

. at least .several hundred years. He also notes a retreat of the glacier front of about 3 miles 

since the ash fell. 

During the summer of 1914 the writer made observations in White River basin that 

afford an opportunity for a more accurate calculation of the time that has elapsed since the ash 

fell-. On White River, about 25 miles northwest of the supposed center of eruption, an excellent 

exposure shows a deposit of 39 feet of peaty vegetable material, interrupted 7 feet below its top 

by a 2-foot layer of ash (Pl. VI, 0). The peculiar appearance of the roots of spruce trees growing 

on the surface of the peat suggested the possibility of determining the rate of peat accumulation 

at that place. The ordinary spruce tree of this region has a fiat root base and sends its roots 

out radially, parallel with the surface. The roots penetrate only a few inches below the surface · 

of the ground. In the locality just mentioned, however, each spruce tree has a central stem 

root, some of them several feet long, from which roots branch off at irregular intervals, including 

an upper set of roots near the surface, corresponding to those of the normal tree. The lower 

roots are in permanently fr:ozen ground, and only the upper ones are functioning. It therefore 

seems evident that the trees as they grew were surrounded by a constantly thickening layer of 

vegetable material. In this material the level of ground frost rose as the deposit increased in 

thickness, the lower roots of the trees became permanently frozen, and the trees were forced to 

, throw off adventitious roots near the surface repeatedly, in their efforts to survive. This study, 

details of which have been published elsewhere/ showed that dividing the age of a living tree, as 

indicated by the annual rings, by the thickness of the peaty deposit above the lowest roots 

gives a rate of accumulation of the peat of about 200 years to the foot. 0 -n that basis the volcanic eruption that caused the ejection of the widespread sheet of volcanic ash in the upper 

Yukon basin took place approximately 1,400 years ago. 

Although perhaps the most recent volcanic eruption within the Yukon basin, the White 

River eruption offers by no means the only evidence of comparatively recent volcanic activity 

in that district, where lavas that were poured out subsequent to an earlier stage of Pleistocene 

glaciation are extensively developed. On the east branch of Dennison Fork of Fortymile River 

a volcanic crater, with associated lava flows, is so young that it still retains much of its original 

topographic form, and Quaternary lavas have been recognized elsewhere. 

1 Capps, S. R.: An estimate of the age of the last great gladation in Alaska: Washington Acad. Sci. Jour., vol. 5, pp. 108-114, 1915. 
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.