APR] CHEMICAL BASIS OF THE ANIMAL BODY. 753 



it maybe formed synthetically 1 by tlie action of sarcosin and cyanamide: 



C 3 H 7 NO 2 + CH 2 N 2 - C 4 H 9 N 3 O. 



Sarcosin is glycin in which one atom of hydrogen has been replaced by 

 the alcohol radicle methyl, thus : 



C H 3 ) C 2 H 2 (CH 3 )O ) _ 



like glycin, Farcosin has not been found in a free state in the body. 



Kreatinin. C 4 H 7 N,O. 



This, which is simply a dehydrated form of kreatin, occurs normally 

 as a constant constituent of urine and of muscle extract. It crystallises 

 in colourless shining prisms, possessing a strong alkaline taste and 

 reaction. It is readily soluble in cold water (1 in 11 -5), also in alcohol, 

 but is scarcely soluble in aether. It acts as a powerful base, forming 

 with acids and salts compounds which crystallise well. Of these the 

 most important is the salt with zinc chloride (C 4 H 7 N 3 O) 2 Zn CLy It is 

 formed when a concentrated solution of the chloride is added to a not 

 too dilute solution of kreatinin. Since the compound is very little 

 soluble in alcohol, it is better to use alcoholic rather than aqueous 

 solutions. It crystallises in warty lumps composed of aggregated 

 masses of prisms, or fine needles. 



Preparation. Either by the action of acids on kreatin, or from 

 human urine by concentrating, and precipitating with lead acetate; in 

 the nitrate from this, a second precipitate is caused by the addition of 

 mercuric chloride, and consists of a compound of this salt with kreatinin. 

 The mercury is removed by sulphuretted hydrogen, and the kreatinin 

 purified by the formation of the zinc salt, and washing with alcohol. 



Kreatinin-zinc chloride may he converted into kreatin, by the action of hydrated 

 oxide of lead on its boiling aqueous solution. 



Allantoin. C 4 H 6 N 4 3 . 



The characteristic constituent of the allantoic fluid of the foetus; it 

 occurs also in the urine of animals for a short period after their birth. 

 Traces of it are sometimes detected in this excretion at a later date. 



It crystallises in small, shining, colourless prisms, which are taste- 

 less and odourless. They are soluble in ] 60 parts of cold, more soluble 

 in hot water, insoluble in cold alcohol and aether, soluble in hot alcohol. 

 Carbonates of the alkalis dissolve them, and compounds may be formed 

 of allantoin with metals but not with acids. 



Allantoin, as already stated, p. 750, is one of the products of the 

 oxidation of uric acid, and by further oxidation gives rise to urea. 



1 Sitzungsber. d. bvjersch. Akad. 1868, Hft 3, S. 472. 

 F. 48 



