440 
Proceedings of the Royal Society of Edinburgh. [Sess. 
XXIX. — Equilibrium in the Ternary System: Water, Potassium 
carbonate, Potassium ethyl di-propyl-malonate. By J. W. 
M>David, B.Sc., Carnegie Research Scholar. Communicated by 
Professor James Walker. 
(MS. received April 13, 1910. Read May 16, 1910.) 
During the electrolysis of a solution of potassium ethyl di-propyl-malonate 
it was discovered by Crichton * that when a concentrated aqueous solution 
of the salt was shaken up with a concentrated aqueous solution of potassium 
carbonate two distinct layers were formed. The peculiarity of this case 
lies in the fact that both substances are salts of the same metal, though 
cases of the non-miscibility of aqueous solutions of two totally different 
substances are common, as, for example, that of potassium carbonate and 
alcohol. 
The object of the following investigation is to show how the miscibility 
of the two solutions depends on their concentrations, temperature, etc. 
The potassium ethyl salt was prepared from di-propyl-malonic ester by 
half saponification with a solution of potassium hydroxide in methyl 
alcohol. The saponification was done in four stages, one-fourth of the 
amount of alkali necessary for half saponification being used each time. 
After addition of water the unsaponified ester which separated was removed 
by means of ether and the aqueous solution evaporated to dryness. The 
potassium ethyl salt was freed from di-potassium salt by dissolving in hot 
absolute alcohol in which the latter salt is practically insoluble. The ester 
salt so obtained was analysed, but was still found to contain a small 
quantity of di-potassium salt. A fresh sample was made as above described, 
but the saponification was only carried out to the third stage. The ester 
salt, purified as before, was found on analysis to be free from di-potassium 
salt. 
02164 gm. potassium ethyl salt yielded 0’0744 gm. K 2 S0 4 ; 
i.e. 100 parts ,, ,, „ 34*37 parts „ 
Theory — 
100 parts KC n H 19 0 4 yield 34*27 parts K 2 S0 4 . 
An attempt was made to determine the solubility of the pure potassium 
* Journal Ghem. Soc., vol. lxxxix. p. 929 (1906). 
