CHEMICAL BASIS OF THE ANIMAL BODY. 



903 



com- 

 ro- 



precipitate is caused by the addition of mercuric chloride, and consists of a co 

 pound of this salt with kreatinin. The mercury is removed by sulphuretted hyd 

 gen, and the kreatin purified by the formation of the zinc salt and washing with 

 alcohol. 



Kreatinin-zinc chloride may be 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 some- 

 times detected in this excretion at a later date. 



It crystallizes in small, shining, colorless prisms [Fig. 242] , which are tasteless 



[FIG. 242. 



[FiG. 243. 



FIG. 242. Crystals from Concentrated Urine of Calf, showing in Centre a Large Bundle of 

 Prisms of Allantoin. (After Ktthne.)] 



FIG. 243. Hypoxanthin-silver-nitrate, C 6 H 4 N 4 O.AgNO3. (Krukenberg, after Kuhne.)] 



and odorless. They are soluble in 160 parts of cold, more soluble in hot water, 

 insoluble in cold alcohol and ether, soluble in hot alcohol. Carbonates of the alka- 

 lies dissolve them, and compounds may be formed of allantoin with metals but not 

 with acids. 



Allantoin, as already stated, p. 901, is one of the products of the oxidation of 

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



Preparation. This is best carried out by the careful oxidation of uric acid, either 

 by means of potassic permanganate or ferrocyanide, or by plumbic oxide. 



Hypoxanthin or Sarkin. C 5 H 4 N 4 O. 



Is a normal constituent of muscle, occurring also in the spleen, liver, and medulla 

 of bones. In lukaemia it appears in the blood and urine. It crystallizes in fine 



[FIG. 244. 



Hypoxanthin-nitrate, C 6 H 4 N 4 O.HNO 3 . (Kuhne).] 



needles which are soluble in 300 parts of cold, more soluble in hot water, insoluble 

 in alcohol, soluble in acids and alkalies. It forms crystalline compounds with acids 



