1275 
The second way of preparing g-truxillie acid did, however, not 
seem difficult, if only a sufficient quantity of a//ocinnamic acid were 
at disposal. 
Owing to the researches of STOERMER*) to whom belongs the credit 
-of having found an easy method for the preparation of the a//o-form 
of cinnamic acid and its derivatives, it was possible to prepare the 
allo-acid from cinnamic acid with the aid of sunlight. A solution 
of sodium cinnamate was exposed daily in large bottles to sunlight 
and after a few months the alloeinnamic acid was isolated in the 
usual manner as the aniline salt. In this manner, I came, in a short 
time, in possession of a fairly large quantity of a//ocinnamic acid. 
As the conditions, in which the most advantageous formation of 
B-truxillie acid takes place, were not yet known, it was first of all 
ascertained what influence can be exerted by different factors. 
For these experiments I used porcelain dishes. The a//ocinnamic 
acid was dissolved and by evaporating the liquid and moving the 
dish thus allowing it to spread all over the sides of the dish, the 
distribution of the acid over the surface was made as even as possible. 
The exposure to light took place simultaneously and for the same 
length of time. 
After the end of the exposure the product was treated as follows. 
The acids were dissolved in dilute ammonia and this solution was 
precipitated with barium chloride. After 24 hours the precipitate 
was collected, washed and the g-truxillic acid liberated by means of 
hydrochloric acid. The filtrate from the barium salt was acidified 
with hydrochloric acid, the precipitate collected, washed and dried. 
By heating with benzine the cinnamic acid was separated from the 
a-truxillic acid. 
It was found that the fusion of the qa//ocinnamic acid (which 
readily takes place in sunlight) was prejudicial to the formation 
of B-truxillie acid as it causes the acid to collect in droplets. Hence, 
in the other experiments the dishes were kept cold by allowing 
them to float upon water. 
The size of the surface over which the acid was distributed also 
exerted an influence, which will be readily understood, as a small 
surface receives in the same time less light than a large one. 
Also in sunlight, iu the same time, more g-truxillie acid was 
formed than in diffused daylight. 
The covering with a glass plate impeded the formation of 3-truxil- 
lic acid. 
1) Ber. 42, 4865 (1909) 44, 637 (1911). 
