392 SCIENCE PROGRESS 



important contribution to the theory of alkaloid synthesis, but 

 it may be pointed out, before leaving this subject, that the 

 starting materials for building up all these complex substances 

 are formaldehyde, ammonia, aminoacids and acetone dicarb- 

 oxylic acid, the first three of which are of course generally 

 assumed to be present in the plant, while the latter may be 

 produced by the oxidation of citric acid, although other possible 

 sources are also indicated. 



Three papers dealing with the Pungent Principle of Ginger 

 are published consecutively in the same number of the Journal 

 of the Chemical Society, one coming from Japan and the other 

 two from Manchester. The first paper, by Nomura (/. Chem. 

 Soc. 191 7, 769), deals with the identification and synthesis of a 

 new ketone Zingerone isolated from ginger by extraction with 

 ether and shaking the extract with 2 per cent, sodium hydroxide. 

 The ketone was proved to have the constitution represented by 

 the following formula, 



CH3O 



HO/~~\ CH 2 . CH 2 . CO . CH 3 



and a number of its reactions and derivatives are described. 

 Lapworth, Pearson and Royle (/. Chem. Soc. 191 7, 777) have 

 also succeeded in isolating the same ketone, but have shown 

 that it probably does not occur as such in the ginger, but 

 is in reality a constituent of the oleo-resin gingerol, which is the 

 true pungent principle of ginger, and that it is combined with a 

 saturated aliphatic aldehyde, as indicated by the formula 



CH s O 

 HO (~~y CH 2 . CH 2 . CO . CH 2 . CH(OH) . [CH 2 ] 7 . CH 3 



This substance is readily hydrolysed by baryta and other 

 alkalies, and the fact that Nomura treated his ether extract 

 with caustic soda would account for his obtaining the Zingerone 

 apparently directly from the ginger. 



The question of the constitution of the urea molecule is 

 once more raised by Werner (/. Chem. Soc. 191 7, 863), who has 

 subjected the reaction between urea and nitrous acid to a careful 

 study, as a result of which he finds that the generally accepted 

 equation 



CON 2 H 4 + 2 HN0 2 = C0 2 -f N 2 + 2H 2 



