NOTES
Dec., 1958
1595
TABLE I Temp.,
ox.
760.0 776.6 811.7 822.6 875.3 928.0 954.7 975.3 993.0 1003.1 1026.1
Vapor pressure of CdClz P,mm. Obsd. Calcd.
0.1285 .2316 ,8026 1.150 4.09 12.17 18.86 27.21 36.07 43.13 59.98
0.129 ,239 ,804 1.15 4.18 11.76 19.02 27.08 36.24 42.61 60.87
Dev.,
Temp.,
-0.4 -3.0 -0.2 0.0 -2.2 +3.4 -0.8 .5 - .5 +1.2 -1.5
695.4 706.3 744.1 776.5 819.7 825,8
%
Vapor pressure of ZnCh P,mm. Obsd. Calcd.
I.077 1.399 4.744 11.63 35.34 40.61
1.03 1.48 4.73 11.72 35.18 40.70
Dev.,
9%
t4.3 -5.7 +0.3 - .9 .5 .2
+ -
+
a transpiration method essentially the same as that described by Sense, et aZ.l Details of our method will be given by Barton and Bloom.2 Dry argon was used as the carrier gas after being carefully deoxygenated over heated copper gauze. The molten salt was contained in three silica boats in a silica tube, heated in a rhodium-platinum wound furnace. Temperature was measured by 13% Rh-Pt us. Pt thermocouples. The cadmium chloride was prepared by direct synthesis3 while the zinc chloride was prepared by heating the pure "anhydrous" salt while passing through it dry HC1 gas to remove water and later, dry nitrogen to remove dissolved HC1. To analyze the transported salt, the method of Barton, Bloom and Richards4 was used for CdClz and a standard volumetric chloride determination method for ZnClz. Results are given in Table I. The fallowing P-T relationships were obtained (assuming t h a t the vapor is monomeric in each case) by the method of least squares CdClz: From 760.0-822.6"K. (solid) log P(mm.) = 11.5753 - 9,472.4/T("K.) AH sublimation = 43.31 kg. cal. mole-' From 875.3-1026.1"K. (liquid) log P(mm.) = 8.5371 = 6,929.O/T("K.) AHvaporiaation= 31.70 kg. cal. mole-' ZnClz: 695.4-825.8"K. (liquid) log P(mm.) = 10.1233 - 7,030.6/T("K.) AHvsporiZation= 32.15 kg. cal. mole-'
OK.
(1) (2)
The authors wish to acknowledge the assistance of the University of New Zealand Grants Committee in the purchase of the apparatus used.
THE SOLUBILITY OF SOME SALTS OF SODIUM, POTASSIUM, MAGNESIUM AND CALCIUM IN FORMAMIDE BY ERVINCOLT ON^ AND ROBERTE. BROORER International Minerals and Chemical Carp., Skokie, 111. Received June 23, 1968
Inorganic salts are generally soluble in solvents of high dielectric constant because the polar nature of the solvent molecules permits solvation of the solute ions. Although water with a dielectric constant of 80.4 a t 20" is used almost universally as a solvent for numerous chemical reactions involving salts, it becomes necessary occasionally to employ non-aqueous media for particular reactions. A non-aqueous, water-like solvent now available commercially is formamide, HCONH2, with a dielectric constant of 84 a t 20'. Since no solubility data are available for salts in formamide, it was of interest to measure the solubility of a number of common alkali and alkaline earth salts in this solvent in order to compare solubilities with those observed in water.
Experimental Chemicals.-All salts were reagent grade chemicals. grade formamide was purchased from Fisher The vapor pressure results compare favorably Reagent Scientific Go. and was used without further purification. with those obtained by the boiling point (ie., the The freezing point of 2.50" agreed well with the literature absolute) methods of Barton and Bloom5 (CdCL) value of 2.55°.2 Solubility Procedure.-Solutions of the salts in formamide and Bloom, Bockris, Richards and Taylor6 (ZnClz). were prepared in glass containers so that an excess of solid This indicates that the assumption that the vapor was always present. After tumbling for a minimum of 48 consists of monomeric molecules is correct for both hours in a water-bath maintained at 25 f l o ,the solutions salts. were filtered quickly and aliquots taken for analysis. The melting point of CdC12,837'K., was obtained Duplicate samples were run, and results are probably mto 3t1yo. Since formamide is somewhat hygrofrom equations 1 and 2. From the heats of sub- curate scopic, a greater degree of precision on solubility measurelimation and vaporization of CdC12, the heat of ments can be obtained only by carrying out all solution fusion, AH fusion = 11.61 kg. cal. mole-l, is ob- transfers in a dry box. Analytical Methods. Potassium.-Potassium could not tained. be determined in formamide with either tetraphenylboron (1) I
