751 



think that also these experiments are eontirmatorj of the hypothesis 

 that the action of pepsin is not determined by the H-ion-coneentiation 

 alone, but principally by the condition of the substratum and in the 

 first place by the swelling. 



Of course the experiments with protein-solutions have to be continued 

 and extended to other acids and here also the influence of salts has 

 to be studied. 



It is perhaps hardly necessary to add that other enzymes have to be 

 subjected to similar observations. The curve representing the viscosity 

 and consequently also the swelling as a function of pn is strikingly 

 analogous to the curve representing the action of many hydrolilic 

 enzymes as a function of pn ; as with trypsin and also with ptyalin '). 

 We are, therefore, inclined to believe that with these enzymes also 

 the condition of the substrata plays a prominent part. 



Chemistry. — "Tlie action of sun-light on the clnnandc ncids." 

 By Dr. A. W. K. de Jonü. 



(Gommunicated ii\ the meeting ol' September 25, 1915). 



For the continued research of a- and ^^-''Storax" cinnamic acid it 

 was necessary to possess a method by which large quantities of the 

 ö-acid can be readily converted into the ,j-acid. 



The rapid evaporation of an alcoholic solution spread in a thin 

 layer on glass plates certainly provides the means of preparing the 

 /J-acid on a small scale, but in this manner one is obliged to always 

 work with small quantities of solution, as otherwise crystals of the 

 «-acid soon occur beside those of the /?-acid. 



According to Eklenmeyf.r Jun.') the i^acid is formed in the 

 following ways'). 



«(-"Storax" cinnamic acid is dissolved in as little ether as possible 

 and precipitated with petroleum ether. If the ethereal solution is not 

 sufficiently concentrated «-acid only, or else a mixture of the two 

 acids, is formed. 



A warm solution of the «-acid in dilute (757(,) alcohol deposits 

 on cooling the p'-acid. 



1) Vide Van Trigt and Ringer's publication in the Proceedings of tlie meeting 

 of Nov. 30, 1912, Vol. XXI. Part. 1, p. 858 (1912). 



2) Ber. 39, 1581 et seq. (1906). 



') In what manner Lehmann has prepared the (3-acid, I have not been able 

 to trace as the original literature is not obtainable in Java. 



