INDUSTRIAL A N D ENGINEERING CHEMISTRY
74
rials. A. G. Aitchison and W. J. Riley of that company entered into many constructive discussions and supplied the production data. E. F. Schweitzer made some of the measurements and calculations. The authors are greatly indebted to E. J. Serfass for carrying out the gas microanalysis. LITERATURE CITED
(1) Betz, L. D., Noll, C. A., and Maguire, J. J., IND.ENQ.CHEM., 32, 1323 (1940). (2) Brunauer, S., “The Adsorption of Gases and Vapors”, Vol. I, p. 120,Princeton Univ. Press, 1943. (3) Ibi‘d., p. 160. (4) Ibid., p. 287. ( 5 ) Brunauer, S., Deming, L. S., Deming, W. E., and Teller, E., J . Am. Chem. SOC.,62, 1723 (1940). (6) Brunauer, S., Emmett, P. H., and Teller, E., Ibid., 60, 309 (1938). (7) Biissem, W.,and Kaberich, F., 2. physik. Chem. 17B, 310 (1932). (8) Cassidy, H.G., J . Am. Chem. SOC.,62,3075 (1940). (9) Castonguay, T.T.,Ph.D. thesis, Iowa State College, 1941. (10) Elvolve, E., Pub. Health Repts., 52, 1308 (1937). (11) Emmett, P. H.,Proc. Am. SOC.Testing Materials, 41,95 (1941). (12) Emmett, P. H., and Brunauer. S., J . Am. Chm. Soc., 56, 35 (1934); 59,310 (1937).
Vol. 39, No. 1
Foster, A. G., Trans. Faraday SOC.,28,645(1932). Giauque, W. F., and Clayton. J. 0..J . Am. Chem. SOC..55, 4875 (1933).
Harkins, W. D.,,and Jura, G., Ibid., 66,1360-72 (1944). Harness, C. L., and Jensen, Nan C., U . S. Bur. Mines, C ~ T C . 7269,14 (1943).
Kraemer, E. O., in Taylor’s “Treatise on Physical Chemistry”, p. 1661,New York, D. Van Nostrand Co., Inc., 1931. McBain, J. W., J . Am. Chem. Soc., 57,699 (1935). Mantell, C. L.,“ildsorption”, New York, McGraw-Hill Book Co., Inc., 1945. Marton, L., J . Applied Phys., 16, 137 (1946). Orr, W.J, C., PTOC. Roy. SOC.(London), 173A,349 (1939). Pauling, L.,”The Nature of the Chemical Bond”, 2nd ed., p. 393,Ithaca, Cornel1 University Press, 1940. Ries, H. E., Jr., Van Nordstrand, R. A, and Teter, J. W., IND. ENG.CHEY.,37,310 (1945). Rubinshtein, A. M., Bull. acad. sci. U.R.S.S., Classs sCi. chim., 1943,427-34.
Seaton, M. Y., Am. Inst. Mining Met. En~rs.,148, 22 (1942); U. 9. Patents 2,219,725-6(1940). Strain, H.H., “Chromatographic Adsorption Analysis”, New York, Interscience Publishers, Inc., 1942. PRESEXTIDD before the Division of Colloid Chemistry at the 110th Meeting of the AMERICANCHEMICAL SOCIETY, Chicago, 111. Based on thesis presented by William C.Walker to Lehigh University in partial fulfillment of the requirements for degree of doctor of philosophy, 1946.
Solubilities of Ammonium and
‘
Potassium Alums in Water ,
DENSITIES OF THE SATURATED SOLUTIONS David Schlain, John D. Prater, and S. F. Ravitz U. S. Bureau of Mines, Salt Lake City, Utah
T h e solubilities of ammonium and potassium alums in water at 0” to 85“ C. and the densities of the saturated solutions at the saturation temperatures have been determined. The results indicate that many of the previously published solubility data, especially on ammonium alum, are incorrect.
T
HE crystallization of an alum is an important step in two of
the processes being investigated by the Bureau of Mines for the production of alumina from sources other than bauxite. Ammonium alum is formed in hhe ammonium sulfate process for recovering alumina from clay ( I d ) , and potassium alum is formed in the recovery of alumina from alunite (1). During a recent study of the distribution of impurities in the crystallization of these alums, data were obtained that were inconsistent with solubilities reported in Seidell (IS) and in the International Critical Tables (7, 8). Moreover, adequate data could not be found on the densities of saturated alum solutions. It was therefore decided to determine the solubilities and densities at 25” to 85” C., the temperature range of importance in connection with the processes’.
-
1 After this article had been submitted for publiostion, it became necessary to make solubility and density determinations at lower temperatures. The smoothed values derived from the additional measurements are as follows:
0 20 lo
63.6 73.4 102
0.0592 0.0810 0.113
1.0268 1.0347 1.0464
54.6 76.0 103
0,0675 0.0802 0.109
1.0283 1.0392 1.0518
A diagram of the apparatus used is shown in Figure 1, Most of the solubility determinations were made from the oversaturation side. Sufficient recrystallized C.P. alum was dissolved in hot distilled water to give a solution containing about 200 grams of alum per liter in excess of the quantity required for saturation at the temperature being studied. The solution was then cooled with agitation to about 1“ C. above that temperature and placed in the covered crystdlizing vessel in the thermostat, where it was cooled to the temperature and aged for 2 hours with constant agitation. With the aid of compressed air, the resulting slurry was filtered through the fritted glass disk in the bottom of the vessel, and the filtrate was transferred to the receiver; the compressed air was first heated to the temperature of the thermostat and saturated with water vapor. A sample of the saturated solution was removed from the receiver by means of a calibrated 100-ml. pipet and allowed to cool to room temperature with agitation. Two hours were allowed for equilibrium to be reached, after which the crystals were filtered off, dried at approximately 42”C., and weighed. The total volume of mother liquor was measured, and its alum content was determined by evaporating an aliquot portion to dryness at 42’ C. and weighing the resulting crystals; this direct determination was checked by analyzing the mother liquor for alumina. The weight of alum in the mother liquor was added to the weight of crystals obtained in cooling the original saturated solution to room temperature, t o obtain the total weight of alum in the saturated solution. As a check on the attainment of equilibrium, a number of determinations were made from the undersaturation side by placing distilled water and an excess of alum directly in the crystallizing
January 1947
I N D U S T R I A L A N D E N G IN E E R I N G C H E]M I S T R Y
75
as those from oversaturation; this indicates that, in general, equilibrium had been attained. Data, taken from the curves at regular temperature intervals are summarized in Table 111, in which the solubility data are expressed as grams and moles of hydrate per 1000 grams of solution'. The values obtained for the solubility of ammonium alum are much lower than those given in Seidell (IS) and in the International Critical Tables (Y), the difference ranging from 30% at 30" t o 2.5% a t SO" C. The data in both references are based largely upon the work of Poggiale ( I I ) , who conducted his tests more than 100 years ago and did not use a thermostat. A recent determination a t 25" C. by Hill and Kaplan (5) is only 1% lower than the corresponding value in Table 111. For potassium alum the solubility data in Seidell (IS) and in the International Critical Tables (8) for the range 25" to 60" C. are based chiefly upon Berkeley's work (2) and agree rather well with the results obtained in the present investigation. Above 60 C., however, the data in Seidell, which appear to be based on Mulder's work published in 1864 (IO), differ greatly from those in the Internptional Critical O
Figure 1.
Thermostat
vessel, agitating the mixture for 2 hours, and then proceeding as described. The results agreed well with those obtained from oversaturation. Careful ammonia analyses of various samples of ammonium alum crystals dried a t 42 " C. indicated that drying had been complete and that no dehydration of the crystals had occurred, since the analyses agreed within 0.1% with the theoretical value for (NH4)zS04.Alz(S04) 3.24H20. The hot, saturated solutions of alum frequently became slightly cloudy because of hydrolysis. To determine whether the extent of hydrolysis was sufficient to affect the solubility determinations, samples of saturated solutions were agitated for 2 hours a t various temperatures from 25"t o 85" C. and filtered, and the residues were washed, ignited, and weighed. The weights showed that only 0.01 to 0.1% of the ammonium or potassihm alum in the saturated solutions had hydrolyzed. ' Temperatures were measured to 0.1 " 6. with a calibrated thermometer, crystals were weighed to the nearest 0.01 gram, and pipets were calibrated with distilled water a t the temperatures a t which they were to be used. The precision of the various measurements was such that, aside from the attainment of equilibrium, the probable errors in the solubility determinations ranged from 0.270 a t 25 to 0.4% a t 85' C. for ammonium alum, and from 0.2%a t 25 to 0.8%a t 85"C. for potassium alum. ?'he densities of the saturated solutions used for the solubility determinations were measured a t the saturation temperatures with 10-ml. pycnometers calibrated with distilled water at the temperatures a t which they were t o be used. Weighings were made to 0.1 mg. and were corrected to vacuo when necessary. The probable errors in the measurements involved in the density determinations range from 0.0005 a t 25" to 0.0056 a t 85" C. for ammonium alum, and from 0.0005 a t 25' to 0.012 a t 85" C. for potassium alum, the greatest source of error being variation of solubilitywith the temperature, which was measured to 0.1 'C.
TABLEI. EXPERIMENTAL SOLUBILITY AND DENSITYRESULTS FOR Temp., O
c.
25.0 34.7a 35.2 40.1 40.3 40.66 40.7a 44.6 44.7" 45.3 50.5 54.5 59.9 . 60.2" 61.2 64.5 64.6" 69.5 74.3 79.0
(NHSzSOa. Alz(S0ds. 24Hz0 Soly., G./L. 126.2
8 0 , Oa
a
AMMONIUM ALUM
107:3 199.3 204.0 200.7 204.0 236.1 234.0
84.5 From below saturation.
269: 5 331.8 390.2 410.2 415.1 438.5 462.4 532 644 723 749 899
Density of Srttd. Soln., G./M1.
1 :Oi45
1.095 1.097 1.097 1,112 1.128 1.150 1.158 1.155 1.178 1.176 1.207 1.236 1.269 1.283 1.329
O
O
RESULTS
The results of solubility and density determinations, expressed as grams per liter and grams per milliliter, respectively, are given in Tables I and I1 and in Figures 2,3, and 4, the unit of volume in each instance being measured at the saturation temperature. Points obtained from undersaturation fit the curves about as well
TEMPERATURE, 'C.
Figure 2.
Solubility of Ammonium Alum
INDUSTRIAL AND ENGINEERING CHEMISTRY
76
Vol. 39, No. 1
1100
1000
p-
900
6
800
1
0
FROM OVER-SATURATION
X
FROM UNDER-SATURATION
700 K
600
2 a
2. c
500 400 300
a
2
200 100 TEMPERATURE, 'C.
'0
10
M
30
40
50
60
70
80
'
90
Figure 4. Densities of Saturated Solutions of Ammonium and Potassium Alums at Saturation Temperatures
TEMPERATURE, O C
Figure 3.
Solubility of Potassium Alum
The International Critical Tables (6) summarize density TABLE11. EXPERIMENTAL SOLUBILITY AND DENSITY RESULTS measurements made by Berkeley (2) on saturated solutions of FOR POTASSIUM ALUM potassium alum a t saturation temperatures up to 60" C., and by Bindel (5), Gerlach (4), and others on supersaturated solutions of Density of Tyz., KzSO~.A1z(SOa)s,24HzO Satd. S o h , ammonium and potassium alums a t 15" or 20" C. The density Soly., G./L. G./MI. data in Table I11 agree within 0.1% with Berkeley's values and 25.2 1,0592 128.0 1.0794 171.5 34.6 are in accord with the values for the supersaturated solutions, if 34.7' 1.0802 172.2 it is assumed that the solutions have the same temperature co1,0808 35.0 1,0946 40.3 iCii.9 efficient of expansion as water. 1,0952 40.5 208.8 40.7" 42.0" 44.8 50.0 55.4 59.9 60.7' 64.4 69.7 75.0 79.4 80.1' 85.0
1,0972
210.5 220.4 250 :4 304.9 358.6 420.4 411.3 461.7 677 720 816 833 1065
1.100
1.111 1.131 1.157 1.182 1.177 1,209 1.252 1.298 1.345 1.355 1,444
' From below saturation. TABLE111. SMOOTHED SOLUBILITY AND DENSITY VALUES FOR AMMONIUM AND POTASSIUM ALUMS Ttmz.,
Soly./lOOO G. S o h . Hydrate, Hydrate, g. moles
Density of Satd. S o h , G./MI.
ACKNOWLEDGMENT
The paper is one of many reporting on various aspects of the Bureau of Mines program directed toward the more effective utilization of our mineral resources. Investigations of our mineral resources are carried out by the Mining Branch, under L. B. Moon, and the Metallurgical Branch, under R. G. Knickerbocker. Both branches are under the supervision of R. s. Dean. The scope of this paper falls in the province of the MetallurgicaI Branch whose activities embrace the separation of difficultly beneficiated ores, the production of pure metals from domestic , deposits, the exploitation 'of marginal ore reserves, the recovery of secondary metals, and the improvement of present industrial metallurgical practice. This paper is published by permission of the Director, Bureau of Mines, Department of the Interior.
(NHa)rSOa.AIz(SOa)a.24HzO 25 35 45 55 65 75 85
120 156 216 296 391 514 692
0.132 0.172 0.238 0.327 0.432 0.567 0.764
1.0521 1.0705 1.0958 1.130 1.179 1.241 1.331
LITERATURE CITED (1)
Baroch, C. T., Hackwood, A. W., and Knickerbocker, R. G., Bureau of Mines Report of Investigations 3845 (Februbry
(2)
Berkeley, Earl of, Trans. Roy. SOC. (London), 203, 189-216
1946). (1904).
KzSOd.AIa(SOda.24HzO 25 35 45 55 65 75 85
1,0586 1.0808 1.111 1.155 1.215 1.297 1.444
Tables, which are based on Marino's work published in 1905 (9). The data in Table I11 for temperatures above 60" C. agree fairly well with those in International Critical Tables but are much lower than those in Seidell, the difference amounting to 20% a t 80 O C.
(3) Bindel, Karl, Ann. Physik, (3) 40,370-98 (1890). (4) Gerlach, G. Th., 2.anal. Chern., 28,466-524 (1869). ( 5 ) Hill, Arthur E., and Kaplan, Nathan, J. Am. Chem. Soc., 60, 550-4 (1938).
International Critical Tables, Vol. 111. PP. 71, 92, 106, New York, MoGraw-Hill Book Co., Inc., 1928.(7) Ibid., Vol. IV, p. 226. (8) Ibid., Vol. IV, p. 242. (9) Marino, L., Gam. chim, ital., 35, 341-64 (1905). (10) Mulder, G. J., "Scheikundige Verhandellingen en Onderzockingen", Vol. 3, pt. 2 , Bijdragen tot de Geschiedenis Van Het Scherkungig Gebonden Water, Rotterdam, 1864. (1 1) Poggiale, M., Ann. chim. phys., 8,463-78 (1843). (12) St. Clair, H. W., Ravitz, S. F., Sweet, A. T., and Plummer, C. E., Trans. Am. Inst. Mining Met. EWTS.,159,255-66 (1944). (13) Seidell, A., "Solubilities of Inorganic and Metal Osganic Compounds", 3rd ed., Vol. I, p, 101, New York, D. Van Nostrand Co., Inc., 1940. (6)
