593 



truxillic acid through heating with acetic acid anhydride could not 

 be explained in another way. 



These exchanges of place of a C^R^- and a COOH-group from 

 one side of the closed-chain to the other side can also take place 

 for the groups of 2 adjacent C-atoms of the four ring, and also 

 of 2 C-atoms placed opposite each other. In one case formula iV 

 is obtained, and in the other case the following formula is valid. 



CooH 



COOH 



This formula is built up from 2 molecules of allo-cinnamic acid. 



The d" truxillic acid now is formed from normal cinnamic acid, 

 viz. through the illumination of the stable lead salt of this acid. ^) 



0,466 gr. of cinnamic acid, as lead salt, gave 0,075 gr. of truxillic 

 acid and 0,095 gr. of 6 truxillic acid after 27 hours' illumination. 



The formula IV must, therefore, be assigned to the 6 truxillic 

 acid, whereas the s truxillic acid possesses the following formula 

 (See form. VI following page). 



By heating with hydrochloric acid at 180^ and also by melting 

 with KOH it is changed into rf truxillic acid. These two acids are 

 in the same relation to each other as fumaric and maleic acid, a is 

 the cis-acid, «f the trans-acid. 



1) Shortly an extensive paper will be published about the action of solar light on 

 cinnamic acid salts. 



