96 
Proceedings of Royal Society of Edinburgh. [sess. 
acid, which was then extracted with ether. The crude acid was 
freed from a small quantity of an oily substance by drying on 
porous tile, and then subjected to systematic fractional crystal- 
lisation from water. We succeeded in separating and purifying 
two acids — one, the less soluble, having the melting-point 193° C., 
the other melting at 120°-121° C. The acids on analysis proved 
to have the same composition, both corresponding to the formula 
c a H 10 o 4 . 
I. T166 gr. more soluble acid gave *2100 gr. C0 2 
and -0737 gr. H 2 0 
II. T350 gr. less soluble acid gave -2432 gr. C0 2 
and -0855 gr. H 2 0 
I Fotmd- ^ Calculated for C 6 H 10 O 4 
C 49-12 49-13 49-31 
H 7-02 7-04 6-87 
The acid melting at 193° would thus seem to be identical with 
the para-s-dimethylsuccinic acid of Bischoff (melting-point 194°); 
and that melting at 120°-121° with his anti-s-dimethylsuccinic acid 
(melting-point 120°). For further confirmation we measured the 
electrolytic conductivity of solutions of the acids, and found the 
following dissociation-constants : — 
Para-acid, K=‘0208 (K=-0205, Bethmann). 
Anti-acid, K= -0138 (K= *0122, Bischoff and Walden). 
In a similar manner we performed the electrolysis of ethyl 
potassium ethylmalonate, and from 150 grams of the salt obtained 
63 grams of an ethereal liquid. The portion of this boiling above 
200°, was saponified, the potassium salt acidified, and the crude 
acid extracted with ether and purified as in the preceding case. 
Besides water as a means of fractional crystallisation, we found 
benzene a useful solvent for effecting the separation of the isomeric 
acids. As before, we obtained in the pure state two acids, 
one melting at 192° €. with decomposition, the other at 130° C. 
Analysis gave the following numbers : — 
I. -1252 gr. acid, melting-point 192° C., gave *2530 gr. C0 2 
and '0915 gr. H 2 0 
