386 CHEMISTBY OF THE LEUCOMAINS. 



through the partial conversion into orthophosphate. Where more 

 accurate results are desired the precipitate can be transferred to a 

 Kjeldahl flask, and the nitrogen determined. The guanin can then 

 be calculated from the amount of nitrogen found. 



Although adenin is precipitated slowly by metaphosphoric acid, 

 it does not interfere with the separation of guanin, since it is soluble 

 in large excess of reagent. Hypoxanthin does not give rise to a 

 difficultly soluble metaphosphate, hence does not interfere with the 

 precipitation of guanin. In the filtrate from guanin metaphosphate 

 the hypoxanthin can be determined directly by Bruhns' hypoxan- 

 thin silver picrate method, though on account of the excess of meta- 

 phosphoric acid in the filtrate it is not to be recommended. It 

 would be better to precipitate the filtrate with aramoniacal silver 

 solution, to decompose the silver salts with dilute hydrochloric acid, 

 and then in the filtrate to separate, according to Bruhns, the adenin 

 from the hypoxanthin. The precipitation of guanin in the presence 

 of adenin should be carried out in very dilute solutions, and, as 

 stated, an excess of reagents should be employed. The method 

 possesses decided advantages over the ammonia method of separa- 

 tion, owing to the solubility of guanin in ammonia, especially when 

 hot. According to Wulff, 100 c.c. of a five per cent, solution of 

 ammonia dissolves in the cold 0.01 g. of guanin. A volumetric 

 method for the estimation of guanin by means of copper was sug- 

 gested by Balke. 



Epiguaniu, CgH^NjO, was isolated from urine by Kriiger and 

 Wolff in 1893, but it was not until five years later that its composi- 

 tion and structure was definitely determined by comparison with the 

 synthetic 7-methyl guanin ^ (p. 341), with which it is identical. This 

 same base was unquestionably isolated by Salomon* as early as 1884 

 from hog's urine ; later from ox urine and leukemic urine. The 

 amount of epiguanin obtained by Kriiger and Salomon ' from 10,000 

 liters of urine is about the same as that of adenin (3.40 g.) and is 

 considerably less than that of xanthin and its derivatives (p. 389). 



It is important to note that this base is probably present with adenin 

 and with xanthin, 1 -methyl xanthin and hypoxanthin in the adrenals 

 (Okerblom*). Kriiger and Salomon incline to the belief that epi- 

 guanin, like the methylated xanthins, results by the cleavage of higher 

 methylated homologues of guanin which are probably present in the 

 food or else it is a constituent of the food and as such passes through 

 the body unchanged. Some epiguanin may unquestionably be de- 

 rived directly or indirectly from the food, but the probable isolation 

 of epiguanin and the separation of 1 -methyl xanthin from the ad- 



^Berichie, 30, 2411 ; 31, 544. 

 'Zeits. physiol. Chem., 18, 207 (1893); 24,!390. 

 *ZeUs. phyniol. Chem., 24, 387; 26, 367, 389. 

 *Zeitx. phyml. Chem., 28, 60, 1899. 



