182 GUANIK 



When pure it crystallises in needles from aqueous solutions. 

 Is soluble in 1086 parts of cold water, readily in hot water, in- 

 soluble in ether, slightly soluble in hot alcohol. Yields crystal- 

 line compounds with acids, also with some salts. The compound 

 with nitrate of silver is soluble in hot nitric acid (sp. gr. 1*1), and 

 is thus separable, together with hypoxauthin, from xanthin. It 

 also yields a readily crystalline compound with picric acid, which 

 is very insoluble in cold water (1 in 3500) and may be used 

 for its quantitative separation from solutions (Bruhns, loc. cit.). 

 It does not give the ordinary reactions characteristic of the 

 xanthin bodies, but like hypoxanthin shows a red colouration on 

 the addition of an alkali after treatment with hydrochloric acid 

 and zinc. 



7. Guanin. C 5 H 5 X 5 0. NH CH 



If H == C C NH 



J JL: 



| \CO (Fischer). 1 



NH C = tf 



It was first obtained from Peruvian guano, which still provides 

 the most convenient source for its preparation. 



The guano is finely powdered and boiled with milk of lime as long 

 as it yields a coloured filtrate. The residue is then repeatedly ex- 

 tracted with boiling solution of sodium carbonate; the filtrate on the 

 addition of acetic acid yields a precipitate of guanin and some uric acid, 

 from which it is separated by boiling with somewhat dilute hydro- 

 chloric acid. A hydrochloride of guanin is formed which is crystal- 

 line, and from this compound the guanin is separated by the addition 

 of concentrated ammonia. 2 



Guanin is also found in small quantities in the pancreas, liver, 

 and muscle extract, and among the products of the action of acids 

 on some nucleins. 3 It may also occur in urine, more especially of 

 pigs, in which case it is also found in many of their tissues ; * ad- 

 ditionally in the retinal tapetum of fishes and in their scales, 5 as 

 also in the integument of amphibia and reptiles, 6 and in vegetable 

 tissues. 7 



It is a white amorphous powder, insoluble in water, alcohol, 

 ether, and ammonia. Its insolubility in the latter distinguishes 



1 loc. cit. (sub xanthin). 



2 Strecker, Ann. d. Chem. u. Pharm. Bd. cxvin. (1861), S. 152. 



3 Kossel, Zt. f. physiol. Chem. Bd. vin. (1884), S. 404. 



4 Pecile, Ann. d. Chem. u. Pharm. Bd. CLXXXIII. (1876), S. 141. Cf. Salomon, 

 Arch. f. Physiol. 1884, S. 175. Arch. f. Path. Anat. Bd. xcv. (1884), S. 527. 

 Virchow, Arch. f. path. Anat. Bde. xxxv. (1866), S. 358, xxxvi. S. 147. 



5 Kiihne u. Sewall, Unters. a. d. physiol. Inst. Heidelb. Bd. in. (1880), S. 221. 



6 Ewald u. Krukenberg, Ibid. Bd. iv. Hft. 3. (1882), S. 253, Zt. f. Biol. Bd. xix. 

 (1883), S. 154. 



7 Schulze u. Bosshard, Zt.f. physiol. Chem. Bd. ix. (1885), S. 420. 



