384 CHEMISTRY OF THE LEUCOMAINS. 



Ethyl guanin, CjH^NjO.CjH,, was obtained by Wulff by heating 

 guanin with ethyl iodid in the presence of sodium hydrate and 

 alcohol. It forms small needle-shaped crystals. When dry it 

 yields a light, dry mass. It is difficultly soluble in water, very 

 difficultly in alcohol, easily in mineral acids. In general it gives 

 the same reactions as guanin. Thus, it yields a silver compound 

 difficultly soluble in ammonium hydrate ; a finely crystalline picrate, 

 etc. The boiling-hot aqueous solution is precipitated by gold 

 chlorid. Apparently it is not altered by heating at 280°. 



Physiologically guanin, like uric acid, is inert (Filehne). This 

 may be due to the extreme insolubility of the base (p. 345). 



Guanin may be readily prepared from Peruvian guano by boiling 

 it repeatedly with milk of lime until the liquid becomes colorless. 

 The residue, consisting largely of uric acid and guanin, is boiled 

 with a solution of sodium carbonate, filtered, and the filtrate, after 

 the addition of sodium acetate, is strongly acidulated with hydro- 

 chloric acid. This precipitates the guanin, together with some uric 

 acid. The precipitate is dissolved in boiling hydrochloric acid, and 

 the guanin then thrown out of solution by the addition of ammonium 

 hydrate. 



A more convenient method of isolation of guanin from Peruvian 

 guano is that of Wulfi^. The guano is boiled with about 5 per cent, 

 sulphuric acid for 4-6 hours, then cooled, and at once filtered. The 

 filtrate is rendered alkaline with sodium hydrate and again filtered. 

 This filtrate, containing guanin and a little uric acid, is now precipi- 

 tated with ammoniacal silver solution. The voluminous precipitate, 

 after standing twelve hours, is transferred to a thick plaited filter, 

 and washed first with cold then with hot water. While still moist 

 the precipitate is removed from the filter and introduced gradually 

 into hot, dilute hydrochloric acid. The silver chlorid is filtered off, 

 and the filtrate digested on a water-bath with animal charcoal. The 

 clear solution is then saturated with ammonium hydrate to precipi- 

 tate the guanin. In order to destroy the traces of uric acid which 

 accompany the guanin the precipitate is dissolved together with a 

 small amount of urea, in boiling 20 per cent, nitric acid, then set 

 aside to crystallize. The nitrate of guanin is now dissolved in dilute 

 sodium hydrate, and reprecipitated by addition of ammonium chlorid, 

 thus removing any traces of xanthin that may be present. 



Inasmuch as the guanin is present in guano in combination partly 

 with calcium, partly as a nuclein-like body, it is not all set free by a 

 single boiling with dilute acid. The extraction should, therefore, 

 be repeated until it ceases to be given off. 



Guanin is also obtained in the decomposition of nuclein with dilute 

 acids, and can, therefore, be prepared from such cellular organs as 

 the spleen, pancreas, etc. It can also be prepared from auto-digested 

 pancreas or yeast (Kutscher), 



