500 
current of dry air at ordinary temperatures (25°—380°). After the 
distillation and after the removal of the remainder of the solvent 
by a dry air current, the flask was closed and placed in ice, where- 
upon after a longer or shorter time crystallisation began. 
The preparation of the allocinnamic acid by subjecting an aqueous 
solution of sodium or potassium cinnamate (containing about 1 °/, 
acid) to light was somewhat modified, so that a more rapid trans- 
formation was attained, and at the same time the unaltered cinnamic 
acid could easily be used again. 
Flat tin-plate vessels were used. In these the solution was set 
out in the daylight, and the water lost by evaporation was made 
up daily. After about eight to fourteen days, exposure the solutions 
were worked up. 
In order to separate out the alloeinnamic acid the solution was 
evaporated to about one tenth of its volume and acidified with 
sulphuric acid when cold. After cooling, the normal cinnamic acid 
was filtered off, washed, and immediately after drying was used 
again for the preparation of a new solution. If this acid melts on 
the water-bath, then allocinnamic acid is still present. This can be 
extracted by means of hot ligroin. The filtrate was neutralised with 
alkali, and the solution then evaporated, until crystals began to form. 
After cooling sulphuric acid was added, which caused the allocinnamic 
acid to separate out as an oil. This is dissolved in ligroin, and the 
solution is allowed to erystallise quietly after ‘seeding’ with the 
68°- or the 58°-acid as required. 
These forms erystallise in large crystals, which even by their 
appearance and also by their melting points are easily distinguished 
from the crystals of the double acid of normal and alloeinnamie 
acids, which occurs only in small quantity. In this way almost 
perfectly colourless crystals are obtained at first which, after recry- 
stallising once from petroleum ether solution, are quite pure. 
Repetition of the above procedure yields crystals with a pale yellow 
colour. These may be decolourised in alcoholic solution by means of 
animal charcoal. 
The water solution can afterwards be extracted with ether and 
yields a further small quantity of impure allocinnamic acid. 
The transformation of the 68°-acid into the 58 acid is easily 
brought about by boiling the erystals with a little water for a 
quarter of an hour. The flask is then closed by means of cotton- 
wool, and the boiling continued. On cooling the alloeinnamie acid 
separates out in oily drops which are transformed into the 42°-acid 
in ice. If the solution with the oily drops is “seeded” with a trace 
