1330
CATHERINE R. EVERTZ AND ROBERT LIVINGSTON
(8) EDWARDS, J. D., A N D STROHM, D. E.: Modern Packaging 19(2), 157 (October, 1945). (9) (a) International Critical Tables, Vol. I, p. 67. McGraw-Hill Book Company, Inc., New York (1926). (b) International Critical Tables, Vol. 111, p. 385. McGraw-Hill Book Company, Inc., New York (1928). (10) KORVEZEE, A. E., A N D MOL,E. A. J.: J. Polymer Sci. 2, 371 (1947). A.: Z . anorg. allgem. Chem. 228, 1 (1936). (11) LANNUNG, (12) MCCREADY, R. M., OWENS,H. S., AND MACLAY, W. D.: Food Inds. 16,794 (1944). R . M., OWENS,H. S., SHEPHERD, A. D., A N D MACLAY, W. D . : Ind. Eng. (13) MCCREADY, Chem. 38, 1254 (1946). (14) PALMER, K. J., MERRILL,R . C., AND BALLANTYNE, M.: J. Am. Chem. SOC.70, 570 (1948). (15) ROUSE,P. E., JR.:J. Am. Chem. SOC.69, 1068 (1917). (16) SCHULTZ, T. H., OWENS,H. S.,A N D MACLAY,W. D . : J. Colloid Sci. 3, 53 (1948). (17) SHUMAN, A. C.: Ind. Eng. Chem., Anal. Ed. 16, 58 (1944). TESTING COMMITTEE: Paper Trade J. 119(4), 29 (July 27,1944). (18) T.A.P.P.I. PAPER
SOLUBILITIES O F SOME ALKALI IODIDES IN ACETONE' CATHERINE R. EVERTZ
AND
ROBERT LIVINGSTOY
School of Chemistry, Institute of Technology, University of Minnesota, Minneapolis, Minnesota Received J a n u a r y 24, 19@
The solubilities in acetone of sodium iodide and of potassium iodide have been determined in the ranges -30" to 60°C. (1, 5 , 7) and -80" to 55°C. (4), respectively. These results and a few scattered measurements of the solubilities of the other alkali iodides suggest that the solubility curves for all of the alkali iodides are similar. To test this assumption, measurements have been made of the solubilities of rubidium iodide and of cesium iodide from about -77" to 35°C. and of sodium iodide from -77" to 21°C. In these temperature ranges the solubilities conform to the general trend of the published data and there is no evidence for the existence of new solvates. MATERIALS
The solvent was prepared from C.P. material by drying overnight with an excess of calcium chloride and distilling through an efficient all-glass fractionating column. Reagent grade sodium iodide was used after being kept a t 50°C. for 4 hr. in a vacuum oven. Rubidium and cesium iodides were prepared by adding an excess of concentrated hydriodic acid to the corresponding carbonates, which were of C.P. grade and were used without further purification. The resulting solutions were evaporated to a small volume and the solid iodides were filtered off a t room temperature. These salts were washed repeatedly with cold dry acetone, and were then dried in a vacuum oven at 75°C. for several hours. 1 This paper is based upon a thesis submitted by Catherine Evertz to the Graduate School of the University of Minnesota in partial fulfillment of the requirements for the degree of Master of Science.
1331
SOLUBILITIES O F IODIDES I N ACETONE APPARATUS AND PROCEDURE
The apparatus and general procedure were similar to those described by Livingston and Halverson (4).Temperature control was improved by the substitution of a simple thyratron relay for the mechanical relay (2) used in the previous work. Temperatures above 0°C. were measured with a 0.1" mercury thermometer, which was calibrated against a U. S. Bureau of Standards certified thermometer. Lower temperatures were determined with a single-junction, triple-strand, copper-constantan thermocouple. The reference junction was kept in melting ice contained in a Dewar flask. The voltage of the thermocouple was measured with a Leeds & Northrup Student potentiometer. The sensitivity of this combination was sufficient to determine the temperature to the nearest 0.5"C. The temperaTABLE 1 The solubility of sodium iodide in acetone TEMPER A T W E
DUBATION OF STIRRING
SOLUBILITY
"C.
hours
weigh1 9cr cent
20.7 0.9 0.5 -21.5 -46.3 -67.3 -62.6 -76.5 -76.5
6.0 6.0 6.5 6.0 6.0 5.0 5.0 4.5 6.0
23.75 11.60 10.83 5.38 2.51 2.20
1.77 1.53 1.55
ture was obtained from the voltage reading by means of the standard equation (6), which was checked a t the sublimation temperature of dry ice. Equilibrium was attained in about 4 hr. when sodium iodide was used. Longer times were required for the less soluble salts-approximately 6 hr. for rubidium iodide and 12 hr. for cesium iodide. EXPERIMENTAL RESULTS
The results of the measurements of the solubility of sodium iodide are summarized in table 1. In the temperature range where they overlap, -30" to 20"C., these results appear to be in reasonable agreement with the published data of Macy and Thomas ( 5 ) , as is illustrated in part by figure 1. Some difficulty was experienced in obtaining the desired percentage accuracy in the measurements of the solubilities of rubidium and cesium iodides, and accordingly a relatively large number of experiments were performed. The points on figure 1 correspond to these original data. Quadratic equations were fitted to these data by an unwejghted least-squares procedure.
X (weight per cent) X (weight per cent)
= =
+
1.15 - 2.13 X 1 0 3 1.54 X 10-4t2for rubidium iodide 0.295 - 3.03 X 10-3t - 2.79 X 10-5t2for cesium iodide
1332
CATHERINE R. EVERTZ AND ROBERT LIVINGSTON
TL MPCRATURL
,
C.
FIG.1. Solubilities of several alkali iodides in acetone in the temperature range -80' to 40°C. NaI: 0, Macy and Thomas (5); 0 , Everts and Livingston. K I : from the data of Livingston and Halverson (4). R b I and CsI: 0 , Everts and Livingston ; e, Lannung (3) ; 8 , Walden (8). TABLE 2 The solubility of r u b i d i u m iodide and of cesium iodide in acetone (rounded values) SOLUBILITY TEMPERATUBE
RbI 'C.
40 30 25 20 0 20 -40 -60 -78.5
-
I
CSI
weight per cent
weight per cent
0.65 0.72 0.79 1.15 1.64 2.25 2.98 3.77
0.13 0.18 0.20 0.22 0.29 0.35 0.37 0.38 0.36
SOLUBILlTIES OF IODIDES IN ACETONE
1333
The standard deviations
corresponding to these empirical equations are 0.10 weight per cent for rubidium iodide and 0.12 weight per cent for cesium iodide. Table 2 summarizes values of the solubilities for a series of temperatures computed with the aid of these equations. The curves in figure 1 representing the solubilities of these salts are plots of the preceding equations. Probably the chief systematic errors in these and in related measurements are due t o failure to attain equilibrium and to the contamination of the materials by water. Since in the present experiments greater care was taken to insure that equilibrium has been obtained than to exclude rigorously traces of water, it is possible that the solubilities (particularly those of cesium iodide) are systematically too high. SUMMARY
The solubilities (weight per cent) of rubidium iodide and cesium iodide in acetone have been measured over the temperature range from (approximately) 40" to -80°C. In this range, the solubility data are fitted by the following equations.
+
S = 1.15 - 2.13 X 10+t 1.54 X 10-4t2for rubidium iodide S = 0.295 - 3.03 X 10-3t - 2.79 X 10-5t2for cesium iodide There is no evidence of solvate formation in this temperature range. For sodium iodide the trisolvate, which is the stable solid phase below 25.7"C., remains stable in contact with the solution down to -78.5"C. REFERENCES (1) BELL,W. R. G., ROWLANDS, C. B., BAMFORD, I. J., AND JONES, W. J.: J. Chem. Soc; 1930, 1927. (2) HEISIG,G. B.: Ind. Eng. Chem., Anal. Ed. 8, 149 (1936). (3) LANNUNG, A.: Z. physik. Chem. A101, 255 (1932). (4) LIVINGSTON, R., A N D HALVERSON, R. R . : J. Phys. Chem. 60, 1 (1946). E. W.: J. Am. Chem. SOC. 48, 1547 (1926). (5) MACY,R., AND THOMAS, (6) SCOTT,R. B. : Temperature-Its Measurement and Control, pp. 208-16. Reinhold Publishing Corporation, New York (1941). (7) WADSWORTH, A. E., A N D DAWSON, H. M.: J. Chem. SOC.192, 2784 (1926). (8) WALDEN, P. T . : Z. physik. Chem. 66, 712 (1902).
1334
FRANK E. YOUNG AND FRANCIS T. JONES
SUCROSE HYDR,ATES THESUCROSE-WATER PHASE DIAGRAM' FRANK E. YOUNG AND FRANCIS T. JONES Western Regional Research Laboratory,2A l b a n y , California
Received J a n u a r y 19, 1949
The work reported in this paper was undertaken as the first step in investigation of phase equilibria of basic importance in the freezing preservation of foods. A survey of the literature (1, 2, 4, 5, 6, 7, 9, 10, 12, 15, 18) indicated that the phase diagram of the sucrose-water system was apparently well established as one involving a simple eutectic of ice and sucrose without hydrate formation. This system was chosen as a starting point, because it offered a n opportunity t o check our technique on a system of importance in freezing preservation. Although the phase equilibrium data in the literature were not always in good agreement, particularly in the vicinity of the eutectic, there was no indication of the complexity subsequently encountered. Apparently no crystalline hydrate of sucrose bas previously been isolated and identified in the solid state, although several types of measurements have been interpreted as indicating the presence of hydrates in aqueous solution (3, 8, 11, 14, 16, 17). Seven previously unreported solid phases have been shown to exist by the well-defined eutectics with ice obtained during this study. Although the data are incomplete because of difficulties discussed later in this paper, solubility curves have been determined for four phases. Additional evidence has been obtained for the existence of three of these phases by microscopic observations and for two of these phases by x-ray difiraction photographs. The data also indicate a complex region below -15"C., the interpretation of which is very uncertain. For convenience in presentation, the material in this paper is re.ported chronologically. EXPERIMENTAL
Sucrose solutions were prepared from distilled water and commercial granulated table sugar containing less than 0.1 per cent impurities. The principal impurities were: moisture, 0.01 per cent; ash, 0.01 per cent; reducing sugars, 0.04 per cent. Three experimental methods were used in this study: solubility measurements, warming curves, and observations with a polarizing microscope. Solubilities were measured refraetometrically on solutions which had been allowed to come to equilibrium from both undersaturation and oversaturation in a 1 Parts of this work were presented a t the 28th Annual Meeting of the Pacific Division of the American Association for the Advancement of Science a t San Diego, California, June 18, 1947, and at the 113th National Meeting of the American Chemical Society a t Chicago, Illinois, April 23, 1948. * Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.
