ELEMENTS OF COMPOSITION. 



43 



Guanin, C S H 5 N 6 . 



Guanin, discovered by Unger in guano, forms with hydrochloric acid 

 a crystalline salt, met with in obliquely pointed needles or parallopipedic 

 tables, belonging in general to the clinorhombic system (fig. 22). Some 

 years ago Strecker obtained xanthin from the transformation of guanin. 

 Guanin is not a constituent of urine, but is found in the pancreas. 



Hypoxanthin (Sarkin), C 5 H 4 N 4 . 



Hypoxanthin of Scherer, which is identical with sarkin, investigated 

 subsequently by Strecker, 

 is seen, by comparison of 

 their respective formula, 

 to be nearly related to 

 guanin, as well as to the 

 substance we are about tc 

 allude to, namely, xanthin. 

 The crystalline forms of 

 their nitric and hydrochlo- 

 ric acid salts (fig. 23) are 

 characteristic, especially the 

 first. Nitrate of sarkin, 

 on rapid separation, forms 

 rhomboidal plates ; slowly 

 deposited, it is met with in 

 tufts of obliquely pointed 

 flat prisms or rhomboidal 

 crystals. Evaporated quiet- 

 ly, large darkly striped 

 bodies like rock crystal are 

 formed, besides smaller 

 cucumber-shaped crystals. 

 The chlorate crystallizes 

 partly in bunches of four-sided bent prisms with curved surfaces, and 

 partly in coarser, irregular, and darker 

 prisms, groupe^ in pairs (Lehmann). 



It has been found in human blood 

 in the disease known as leucaemia, 

 (Scherer) ; in the blood of the ox and 

 horse; in muscle, in the heart, in the 

 liver, spleen, thymus, and thyroid 

 glands (Scherer, Strecker, Gorup-Bes- 

 anez), and, finally, in the kidney and 

 urine. 



Xanthin, C S II,N 4 2 . 



Xanthin, which differs from hypo- 

 xanthin in having one more, and from 

 uric acid one less, atom of oxygen, 

 forms a salt with nitric acid, which 

 crystallizes in bunches of rhombic tables 

 and prisms. Chlorate of xanthin oc- 

 curs in glittering, six-sided tables (fig. 24). 



Xanthin was formerly only known as a constituent of very rare urinary 



Fig. 23. Crystals of nitrate of sarkin (upper half), and of 

 chlorate (lower half). 



Fig. 24. Crystals of nitrate of xanthin 

 (above), and chlorate (below). 



