21 



Furthermore, the action 'of emulsin upon artificial benzaldehyde 

 cyanohydrin was investigated. n g. of the synthetically prepared 

 nitrile, which was faintly lsevorotatory, was kept for three days with 50 cc. 

 water and 0,5 g. emulsin at ordinary temperature, then extracted with 

 ether, the residue of evaporation dissolved in 100 cc. chloroform 

 and its optical behaviour tested in a 2 decim. tube. It was found 

 to show a rotation of -4- o°36'. The aqueous solution contained 

 0,09 g. hydrocyanic acid. As a check-test the experiment was repeated, 

 but without the addition of emulsin. In this instance the rotation 

 observed in a 2 decim. tube was — o°5' and the hydrocyanic acid- 

 content was 0,05 g. According to Auld these experiments prove 

 that the cyanohydrin is first split up and that subsequently, under 

 the influence of emulsin, asymmetric synthesis may take place. 



Recent observations made by Feist 1 ) contradict the views quoted 

 above. In a paper published very shortly after the appearance of 

 that of Auld, Feist dealt with the preparation of the two optically 

 active benzaldehyde cyanohydrins. The lsevorotatory isomeride 

 was obtained, after many fruitless experiments, from artificial, inactive oil 

 of bitter almonds (containing prussic acid), of which the rac. benz- 

 aldehyde- cyanohydrin content was ascertained at 80,8 °/o- This cyano- 

 hydrin was allowed to stand, in dilute alcoholic solution, with emulsin for 

 48 hours at 20 with occasional stirring, while for the purpose of removing 

 the prussic acip a current-of air was passed through. The explanation of 

 the reaction (which is based upon the fact that, to all appearance, emulsin 

 only splits off d- benzaldehyde cyanohydrin) is that the conversion ex- 

 pressed in the following equation is partly accomplished: — 



(d -|- 1) - benzaldehyde cyanohydrin -|- emulsin = 1- benzaldehyde 

 cyanohydrin -J- benzaldehyde -\- hydrocyanide -J- emulsin. 



The liquid was extracted with ether, the evaporation residue weighed, 

 again dissolved in ether and tested as regards its rotatory power, which 

 was found to be a(?[a]) — 1,4°. When the 1-benzaldehyde cyano- 

 hydrin was heated with hydrochloric acid, d-mandelic acid was pro- 

 duced. 



Feist also investigated the formation of d- benzaldehyde cyano- 

 hydrin in the breaking-up of amygdalin and observed that this proceeds 

 quantitatively. Other experiments consisted in preparing benzaldehyde 

 cyanohydrin from amygdalin by means of emulsin by splitting-up, and 

 then producing it synthetically by means of emulsin under similar ex- 

 perimental conditions from hydrocyanic acid, benzaldehyde and glu- 

 cose, in proportions equivalent to amygdalin. The results thus obtained 

 confirmed Feist in the view he had previously expressed 2 ) 



*) Arch, der Pharm. 247 (1909), 226. 



*) Arch, der Pharm. 246 (1908), 206; Report November 1908, 14. 



