1054 



very small crystals was obfaiiied, which, when filtered off and washed 

 with alcohol, gave 241 gr. of cinnamic acid. The product was 

 recrjstallized once more in the same way. The synthetic acid pre- 

 pared fro n tiiis gave a first fraction of 1 gr. from 13.5 gr.. which 

 was nnmistakahly Erlknmkyer's so-called synthetic acid. 



It appears therefore from this investigation that the heterocinna- 

 mic acids of Eklknmeyer Jr. are not obtained by the method 

 described by him from pure cinnamic acid. Their formation is to 

 be ascribed to an impurity in the cinnamic acid which he used. 



The heterocinnamic acids are therefore not pure chemical compounds. 



A remark on the reaction of Beilstkin may i)e made here. Erlen- 

 MEYEH makes the following statement:') "Es mag hier darauf hinge- 

 wiesen werden, dass selbst die best krystallisierte Storaxzimtsaure, 

 welche bei der Prüfung mit Soda und Salpeter sicli chlorfrei eiweist, 

 niit der Kupferoxydperle in der Flamme des Bunsen-Brenners erhitzt, 

 dieser eine intensiv grüne Farbung zu verleihen vermag.'' 



I have also found that ciiuiamic acid, by whatever method it was 

 purified, always gave Beilstein's reaction, all hough only faintly. 



The methylester, even the un purified snbstance, gave no coloured 

 flame reaction when heated with copper oxide. The copper salt is, 

 however, cpiickly formed by healing cinnamic acid and coppei'oxide, 

 and the same salt, pre|)ared from an alkaline solution of the ammo- 

 nium salt by precipitation with copper sulphate, gave the reaction 

 more distinctly than the free acid. 



According to Erlenmeyer Jr., pine copper carbonate also gives 

 the reaction. Possibly the Beilstein reaction is more sensitive for 

 acids than for neutral substances or altogether inaj)plicable in the 

 case of most acids. In the meantime no conclusion can be arrived 

 at since the possibility of the presence of impurity, even in small 

 quantity, in the cinnamic acid used by me is not excluded. 



Buitenzorg, August 1918. 



1) Ber. 43, 956 note. 



