LEUCINE. 145 



not to be compared with the acid oxide- of-ethyl salts, since only 1 

 atom of acid ever combines with leucine; they are, in one respect, 

 most similar to those ethers which may be equally represented as 

 true neutral salts or conjugated acids, as, for instance, the salicylates 

 of oxide of methyl and of oxide of ethyl; but still more to the 

 compounds of the alkaloids with neutral metallic salts, such as we 

 treated of in our remarks on creatinine. 



Nitrate of leucine } leiiconitric acid, C 12 H 13 NO 4 .HO.NO 5 , sepa- 

 rates in crystals on saturating moderately concentrated nitric acid 

 with leucine ; it has an acid but not sharp taste ; the salts decrepitate 

 on being heated, and some of them are crystallisabta 



Hydrochlorate of leucine, C 12 H 13 NO 4 .HC1, also crystallises 

 readily. 



Leucic acid, C 12 H U O 5 .HO, is not only formed in the above 

 manner by oxidising agents on leucine, but also, when an aqueous 

 solution of this substance has been for a long time exposed to the 

 air, it then developes a nauseous odour, and in the solution we 

 find the ammonia-salt of this acid. It is not crystalline, but 

 oleaginous, dissolves freely in alcohol and ether, and forms crystal- 

 Usable salts with bases. 



Cahours has pointed out the analogy of leucine with the base 

 thialdine, discovered by Liebig and Wohler ; * both bodies contain- 

 ing the same equivalents of carbon, hydrogen, and nitrogen, and the 

 2 atoms of oxygen of the leucinebeing replaced by 2 atoms of sulphur 

 in thialdine. This body is produced when aldehyde-ammonia is 

 brought into contact with caustic ammonia and sulphuretted 

 hydrogen ; it forms large, colourless, rhombic tablets, which fuse 

 readily, but again solidify at 42, volatilise when exposed to the 

 air, and can be distilled unchanged in the presence of water, but 

 not in the dry state ; they are slightly soluble in water, but dis- 

 solve readily in alcohol, and still more so in ether, and exhibit no 

 reaction on vegetable colours. The salts that have been examined are 

 C 12 H 13 NS 4 .HCland C 12 H 13 NS 4 .HO.NO 5 ; this substance also forms 

 compounds perfectly analogous to those of leucine. On dry dis- 

 tillation with hydrated potash its behaviour is very different from 

 that of leucine, since it yields leucoline (otherwise called 

 chinoline.) 



Preparation. According to Mulder, the caseous oxide disco- 

 vered by Proust, and Braconnot's aposepidine, are perfectly iden- 

 tical with leucine. It is principally formed in the putrefaction of 



* Ann. d. Ch. u. Pharm. Bd. 61, S. 1-11. 



