'302 PROFESSOR A. CRUM BROWN AND DR JAMES WALKER ON THE 



metrical dimethylsuccinic acid. Now this acid contains in its molecule two similar and 

 similarly situated asymmetric carbon atoms. It should therefore occur in two isomeric, 

 optically inactive forms, corresponding to racemic acid and inactive tartaric acid respec- 

 tively. These two forms have already been obtained and described by Zelinsky, Hell 

 and Rothberg and others, and have been distinguished by Bischofp by the names para- 

 s-dimethylsuccinie acid and anti-s-dimethylsuccinic acid.* The former is less soluble in 

 water than the latter, so that it is possible to separate them by fractional crystallisation 

 of their aqueous solution. We therefore subjected the acid which we had obtained to a 

 careful fractionation of this kind, because, as the substance from which we started was 

 optically inactive, theory led us to suppose that our product was a mixture of the two 

 possible optically inactive isomers. Experiment proved that this is the case. The less 

 soluble acid, after four recrystallisations, fused (with decomposition) at 193°, which 

 agrees with the fusing-point of para-s-dimethylsuccinic acid. A combustion gave the 

 following results, agreeing with the formula C e H 10 O 4 : 0*1350 gramme gave 0*2432 

 gramme C0 2 and 0*0855 gramme H 2 0. 



Calculated for C 6 H 10 O 4 . Found. 



C . . . 49-31 4913 



H 6-85 7-04 



We determined the dissociation constant with the following result : — 



Para-s-dimethylsuccinic acid, prepared by electrolytic synthesis. 

 COOHCH(CH^CH(CH 8 )COOH. 



^oo =354. 



v p. 100m K 



100 4768 13-47 00210 



200 655 18-50 0-0210 



400 88-3 24-95 0020? 



800 1175 3312 00206 



1600 153-2 43-28 00207 



K = 0-0208. 



Bischoff and WALDENt found the value K = 0*0190, while Bethmann \ from a speci- 

 men prepared by Zelinsky found K = 0*0204. The agreement may be regardou as 

 satisfactory. 



The more soluble acid crystallised from water in beautiful groups of needles fusing at 

 120°-121°. The fusing-point of anti-s-dimethylsuccinic acid was found by Bischoff 

 and Voit to be 120°. A combustion gave the following results agreeing with the formula 

 C 6 H 10 O 4 . 0*1166 gramme gave 0*2100 gramme C0 2 and 0*0737 gramme H 2 0. 



Calculated for C,.H 10 O,,. Found. 



C 4931 4912 



H 685 702 



* Berichte der deutschen chemischen Gesellschafi 21, 2096 and 22, 389. 



t Ibid., 22, 1821. 



I Zeitschrift fur 2>hysihilische Chemie 5, 404. 



