— 139 — 



In order to separate the synthetic cinnamic acid into its component 

 parts, the ethyl ester was subjected to careful fractional distillation in 

 vacuo. After saponification there was obtained, from the fractions with 

 the lowest boiling points, storax cinnamic acid, and from those with 

 the highest boiling points and from the residue the combination for- 

 merly 1 ) described as "new triclinic cinnamic acid", and now as "hetero- 

 cinnamic acid". This combination, like the storax acid, can occur either in 

 the a or the /?-form, and the two forms can be both converted into 

 each other. The acid recovered from the residue by the method of 

 separation above indicated was the /?-form. It occurred as a lustreless, 

 light, chalky powder; m. p. 12 8°. It was more readily soluble in 

 water, ether, alcohol, or ligroin than were either the storax acid or the 

 synthetic acid. The acid was easily convertible into the a-form, which 

 separated out in lustrous, small crystalline flakes, but the hetero-/?- 

 cinnamic acid was less inclined to conversion than was the storax-/?-acid, 

 and it was therefore generally very easy to re-convert the hetero-a- 

 cinnamic acid into the ^S-acid. The m. p. of the hetero-a-acid was 

 130 to 13 1°. In the method of separation by the aid of the esters, 

 as set forth above, the /?-acid was formed from the a-acid by con- 

 version, because the synthetic cinnamic acid was obtainable in its 

 characteristic crystalline form by combination of hetero - a - cinnamic 

 acid and storax-a-cinnamic acid after crystallisation from ether, whereby 

 the proof of its composition was given. The two acids formed mixed 

 crystals in every proportion; but on the other hand, when hetero- 

 /?-cinnamic acid and storax-a-acid were dissolved together, the former 

 was partly converted into hetero-a-acid, so that crystallisations of 

 altogether different characteristics were obtainable. No uniform mixed 

 crystals were observed in this case. 



A further paper 2 ), connecting with that abstracted above, discusses 

 the differences in chemical behaviour of the isomeric acids obtained 

 from synthetic cinnamic acid as regards the formation of salts and the 

 additive reactions. Without entering into details, we will only mention, 

 that besides salts which showed great exterior resemblance, others 

 were obtained which presented marked differences. In the matter of 

 additive reactions, the two acids distinguished themselves by considerable 

 divergence in the rate of speed of the reactions. By means of frac- 

 tionated precipitation of the sodium salt with hydrochloric acid it was 

 furthermore possible, owing to the difference in strength of the two 

 acids, to devise a process for splitting-up the synthetic acid into its 

 two component parts. Worthy of note also is the property possessed 

 by storax acid, synthetic cinnamic acid and hetero-/?-acid, as mono- 

 basic acids, of yielding acid salts which must be derived from double 



*) Report April 1907, 156. 



2 ) Berl. Berichte 42 (1909), 182. 



