1281 



and solutions are obtained which are in eqnilibriuni with these two 

 modifications. If these solutions are allowed to evaporate in the air, 

 the double acid separates together with the modification of the allo- 

 cinnaniic acid emj)love(l for inoculation. 



The petrol solution, mentioned above, can also furnish solutions 

 answering the purpose, by inoculation with the desired modifications. 



In this waj it is easy to make the double acid crystallise in the 

 presence of large crystals of allo-cinnamic acid of melting point 

 58° or 68°. 



By boiling the warm concentrated petrol solution of the two acids 

 for yj^ hour, it is possible to obtain by cooling the double acid which 

 .separates in the presence of melted acid of m.p. 42°. 



The doul)le acids obtained in this manner were analysed according 

 to the method given in Rec. Trav. chim. 31, 259, when it was 

 found, that all consisted of equal quantities of the acids, as is seen 

 from the following table. A preliminary experiment with 0.0545 grm. 

 alio- and 0.0510 grm. normal cinnamic acid showed that the 20 c.c. 

 of benzene used dissolved 2.25 c.c. N/10 allo-cinnamic acid as 

 aniline salt. 



Double acid 



Quantity 

 taken 

 grm. 



Titration 



Recovered Normal cinnamic 

 dissolved ' acid found 

 cinnamic acid \ 



15 c.c. ! 20 c.c. 



grm. 



grm. 



The various double acids show the same melting intervals; they 

 begin to sinter at about 56° and are fully melted at about 90°^). 



In order to ascertain, whether these varieties of double acids 

 formed in the presence of crystals of allo-cinnamic acid of m.p. 

 58° and 68°, and in a solution, in equilibrium with the acid of 

 m.p. 42°, were identical, an aqueous solution was prepared saturated 

 at room-temperature with respect to both acids, and in equilibrium 

 with the acid of m. p. 42° (in this case also, when working at 



1) Possibly the triclinic allo-cinnamic acid of Erlenmeyer Jun , with m.p. 80°, 

 is the double acid of normal and alio cinnamic acids. Ber. 39, 1571 (1906); 40. 

 662, 663 (1907). Grystallograpliic measurements were not made on account of 

 the absence of the necessary instruments. 



85* 



