:754 UREA AND ITS ALLIES. [Arp. 



Preparation. This is best can led 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 muscles, occurring also in the spleen, 

 liver, and medulla of bones. In leukhsemia it appears in the blood and 

 urine. It crystallises in fine needles which are soluble in 300 parts of 

 cold, more soluble in hot water, insoluble in alcohol, soluble in acids and 

 alkalis. It forms crystalline compounds with acids and bases. It is 

 precipitated by basic acetate of lead, the precipitate being soluble in a 

 solution of the normal acetate. Its preparation from muscle-extract 

 depends on its precipitation first by basic acetate of lead, and then by an 

 ammoniacal solution of silver nitrate after the removal of kreatin. 



Both hypoxanthin aud the next hody, xanthin, can also be obtained from 

 proteids by the action of putrefactive changes, of water at boiling temperature, of 

 dilute hydrochloric acid (-2 p.c.) at 40 C, and by the action of gastric and pancreatic 

 ferments 1 . Chittenden has noticed a peculiar difference between fibrin and egg- 

 albumin when submitted to the above processes ; he finds that the latter does not 

 yield hypoxanthin when treated with boiling water, with dilute hydrochloric acid, or 

 gastric ferment, while the former does. Egg-albumin on the other hand yields 

 hypoxanthin by the action of pancreatic ferment in alkaline solution but not so 

 readily as fibrin does. 



Xanthin. C 5 H 4 N 4 O 3 . 



First discovered in a urinary calculus, and called xanthic oxide. 

 More recently it has been found as a normal, though scanty, constituent 

 of urine, muscles, and several organs, such as the liver, spleen, 

 thymus, <fec. 



When precipitated by cooling from its hot, saturated, aqueous 

 solution it falls in white flocks, but if the solution be allowed to 

 evaporate slowly it is obtained in small scales. When pure it is a 

 colourless powder, very insoluble in water, requiring 1500 times its 

 bulk for solution at 1 00 0. Insoluble in alcohol and aather, it readily 

 dissolves in dilute acids and alkalis, forming crystallisable compounds. 



Hypoxanthin by oxidation becomes xanthin. Both these bodies, as 

 well as the following, guanin and carnin, are evidently closely allied to 

 uric acid; indeed, uric acid by the action of sodium-amalgam may be 

 converted into a mixture of xanthin and hypoxanthin. 



Preparation. It is obtained from urine and the aqueous extract of 

 muscle by a process similar to that for hypoxanthin, and is then 



1 Salomon, Zeitschr. f. physiol. Chem. Bd. n. (1878-1879), S. 60. Krause, Inaug. 

 Diss., Berlin, 1878. Chittenden, Journ. of Physiol. Vol. n. (1879), p. 28. See also 

 Drechsel, Ber. d. deutsch. Chem. Gesell. Jahrg. xin. (1880), S. 240. Salomon, 

 Ibid. S. 1160. Kossel, Zeitsch.f. physiol. Chem. Bd. v. (1881), Sn. 152 u. 267. 



