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V L G i h k k X I N G , 1 UIVERSITY O F W A S H I h G T I ) \
T l t E 1JrP.4KiMi:s 1 1 OF ;"EMICAL
The Solubility of Some Salts in Ethylenediamine, Monoethanolamine and Ethylene Glycd' HI. HEKREKT s. ISf313"' 'The aniino group oi liquid animonia and thv hydroxyl group of water are quite similar in tnnny respects. The many striking analogies between water and liquid ammonia, developed by Franklin and c q - w ~ r k e r shave , ~ led to a widespread interest in liquid ammonia research.6 However, because of the involved experimental technique required in such investigations, other similar polar solvents rnay be preferred. Putnam and Kobe6 have demonstrated that ethylenediamine is a desirable medium for theoretical studies as it is not only comparable in ionizing power to liquid mirnonia, but also possesses more adaptablc physical and chemical properties. Their tabulation of physical properties shows that polar p r o p erties, as dielectric constant! surface tension, dipole moment, etc., ;ti-? coinparable to liquid itininonia. I t is the object oi this work to tieteriiiine thc solubility of a series of typical inorganic salts iii ethylenediamine and compare with solubilit.ies in liquid ammonia and in water. I n addition, c w i i parisons have been made ior the related sc:Ivt.iit.i riionoethanolarnine and e tliylerie glycol. Experimental Preparation of Solvents.-The ethylene glycoi ant1 nionoethanolamine were the technical grade chemical5 of Carbide and Carbon Chemical Corporation and were purified by careful fractionation.: The ethylenediamine was dehydrated and purified by the method previously :i~ed.~ General Treatment of Salts.-Analytical grade salts were used and those not conforming to A. C. S. specifications were purified by recrystallization. Generally, drying at 150" was suficient to remove all water, but the perchlorates were recrystallized from water above 50" and dehydrated at 250'. LiI.3en was prepared from LiI,3H20 by successive crystallizations from anhydrous ethyleneriiamine. Equilibrium-The solvelit and exce5s solid phase were sealed in soft-glass test-tubes and rotated for at least one week in a water thermostat a t 25.0 =t0.08". Analyses of a series of tubes were made a t regular intervals until check values were obtained, which, in ethylenediamine were within 0.5% for salts more soluble than 3 g. per 100 g. of wlvent, though with less soluble salts the differences were a< high as 4y0, For moiioethanolamine arid ethylene ~ l y c o the l data werc more consistent. Analysis of Solutions analyses were made on a wtsight basis by lis? of wc 3 0 t h t.he staridard 1) Paper 11; for I hec wi' i ['resent addre,b. i: ,id i
:?I
I
I
, : . i i s ,
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tiiiirtgisiii
C'.
I 3) Present addresh I>cpnrtmtuc o( (.heni:cai k;ngineermg, Uiii% t r s i t yof Texas, Austin, Texas.
Ethylene glycol 7.15 35.4 107.4 5.18 15.5 49.9 16.0 75.5 1.21 1.03
20.6 36.4 36.8
0.00
17.8
2.07 84.66 170 9.4 10.6 8.0 0.51 142.6 91.5 239 37 9 83 55.8 37.2 7.2 26 (100)
found more soluble in ethylenediamine than in water. The thiocyanates are very soluble and sodium thiocyanate is the most soluble salt reported in both liquid ammonia and ethylenediamine. The solubilities of sodium and potassium nitrates are similar to those of the corresponding bromides. As would be expected from the similarity of ethylenediamine, monoethanolamine and ethylene glycol, solubilities in monoethanolamine tend to occupy a position intermediate between the other two solvents. For the less soluble salts this value approximates the geometric mean of the solubilities in the other two related solvents. For the more soluble salts, the solubilities are unpredictable. The extraordinary viscosity of lithium salts in monoethanolamine is noteworthy. Although no generalizations are apparent as to whether a hydroxyl or amino group will make a better solvent, the ratios of solubilities in ammonia to water are approximated by the corresponding ratios for ethylenediamine to ethylene glycol. These ratios are shown in Table 111. TABLE 111 RATIOS AT 2.5"
%LtlBII.ITY
Approximate, solutions very viscous. TABLE I1 COMPARISON OF SOLVATES
AT
CdWNHzh
25"
Water
Ethylenediamine
NaCl NaBr.2HzO NaI.2H20 KCl KBr KI NaClOs NaClOcHZ0 KClOa KClOi LiCl.Hz0 LiBr.2HzO LiI.3H20 CaC12.6H20 SrC12.6HzO BaC12.2H~0
NaCl NaBr NaI.3en KCI KBr KI NaClOa NaC104.3en KClOs KClOi LiC1.2en LiBr.2en LiI.3en CaClz.6en SrClr.6en BaCls.4en
era1 salts more soluble in liquid ammonia than in water, potassium perchlorate was the only salt
4%
&It
C:IL(OH)a
" ! Ha0
KCl NaCl KBr LiCl KClOa NaI KI NaBr
0.OO27 .046 .050 .097 .12 .32 1.50 1.53
0.0011 ,084 .20 ,017 .29 .882 1.22 1.46
summary 1. The solubilities of a number of inorganic salts have been determined in ethylenediamine, monoethanolamine and ethylene glycol. 2. Although the solubilities in ethylenediamine are less than those in liquid ammonia, the former has been shown to possess similar solvent characteristics. 3. Ammonia/water solubility characteristics are approximated by the corresponding ethylenediamine/ethylene glycol ratios. SEATTLE, WASHINGTON RECEIVEDJULY 25.1944
