ZDANUKAND LOWELL V. COULTER
Vol. i 4
tion ol hydrochloric acid for equal volume extraction given by Nachtrieb and Conway.8 The equilibrium concentrations for initial hydrochloric acid of 9.5, 10.3 and L1.5 molar in Fig. 4 have been calculated for equal volume extraction from tie line data on the ternary diagram. The results of this investigation are being applied iii a study of the ferric chloride extraction system. Acknowledgment.-This investigation is partially supported by the U. S. dtomic Energy Commission under Contract No. hT(30-1)-362. The authors are also indebted to Professors L. G . Bassett, W. H. Bauer and S. E. Wiberley who contributed generously of their time for consultation during the course of this work, and to Mr. J. E. Savolainen who participated in the early stages of the investigation. TROY, NEW Y W ~ K
ter it has passed tlirougli the miniinurn is apparently due to the large concentration of HCl in the organic
solvent. With the continued increase in solubility o f water in the ethereal phase, this la!-er lxcotnes siniilar to the denser phase. i\%ilc the molar distribution coefficient of HC1 Ijctween the two layers, which is shown in Fig. 3 , increases continuously, the equilibrium HC1 concentration reaches a maxinimii and then decreases. This decrease is due to the enhanced solubility of ether in the aqueous phase. The location of a maximum in the equilibrium hydrochloric acid concentration of the aqueous phase suggests an explanation for the decrease in extraction efficiency of ferric chloride by isopropyl ether when the initial hydrochloric acid exceeds 8.; molar. The plot shown in Fig. -1 is very similar in shape tu a plot of the log (I'e)J;t/(Fei.,,, : p i n s t the initial concentra-
[ C O S r K I B L T I O N FRUM THE CHEMICAL LABORATORY O F BOSTONUNIVERSITY]
The Thermochemistry of Calcium and Calcium Iodide in Ammonia at -33'' BY SUMKER P. ~YOLSKY,EDWARD J. ZDANUKAND LOWELL Y.COCLTEK hCE1VED
MAY29, 1032
Pur the solution reactioti of calcium metal :tricl calciurri iodide in liquid ainmonia, AEf = -19.7 atid -62.8 kcal., respcctively, a t - 3 3 '. For the reaction of calcium nietal with NHI'(ainj, A H = -99.3 kcal. From these thermochemical data for calcium metal, A H = -79.7 kcdl. has been calculated for the reaction: ep'(am) 2NH4+(am) = 2NHa(l) Ht(g): This result is in agrecnicnt with that previously obtained for the same reaction based on the thermochemistry of the alkali metals, and signifies two-electron ionization of the cakium atom in ammonia rather than one-electron ionization and the presenceof Cal++previously proposed. In ammonia, S " C a + T = - 129 e x . relative to .SOH+ = 0. If two-electron ionization of calcium is assumed, the solvation energy difference for the gas ion pair, I- and e-, based on the thermochemistry of calcium and calcium iodide is 32.8 kcal. which compares favorably with 31.5 and 31.4 kcal. obtained from the thermochemistry of sodium and potassium and their iodides. The large negative ionic entropy of Ca++(am)and the larger heats of ammoniation of electrolytes compared with heats of hydration are qualitatively correlated with the differences in the nature of the sol vents
+
Moderately dilute solutions of the alkali metals in liquid aiiimonia react with NH4+(ain) according to the equatioii l i p e ? - ( ; r l t l ; 4-S J I J . ( ; t i i i , = SH.(I:4-I !II?!g (11 with the liberation of 40.4 i 1 kcal. per equivalciit.' The const.ancy of this value for thc alkali iiietal solutions has confirmed the observed similarity of the state of the electron it1 these solutions antl, i i i acldition, now serves as a basis for coinparison of tlie alkaline earth metal solutions with the alkali iiietal solutions. This is of particular interest in the case of calcium solutions since the low magnetic susceptibility of these solutions relative to barium sulutions3has been interpreted by Yost and Russell4 as an indication of one-electron ionization for the solution reaction, Ca(s) = i/2Caa++(alllj ',/.ez=(am), rather than two-electron ionization, Ca(s) = Ca++(am) ez=(anij. X s a part of the objective o f this research, i t has been of interest to iiiakc ;t tlierniochemical distinction between the two differe r i t n ~ o d e so f iotiizatioii with the usc r ) f tlic rc-
+
+
(1) Part of this paper was presented before the Division of Physlcal nnd Inorganic Chemistry, Arnrrir;in Chemical Sucirtv Lfeeting. Clr!.eland. Ohio, April 11. l'J.51. ( 2 1 L. V. Coulter and R . LI. hlaybury. ' 1 ~ 1 JsO U R X A L , 71, 3:'~!14 : 1 P i 9 ) ; 1,. V. C o u l t e r and I,. \Conchick, i b i d . , 73, 5867 (1951). ::$I S. I'recd and S . Sugarrnn~i,J . Cheiu. P h y s . , 11, 384 (1943) ( 4 ) Don ?.l. YusC aud Hurace F
