400 CHEMISTRY OF THE LEUGOMAINS. 



sodium and potassium bicarbonate, ammonium bitartrate. Ammo- 

 nium chlorid, nitrate, sulphate, carbonate, oxalate, tartrate, are trans- 

 posed to form sodium salts, and the free bases are thrown down. 

 Similar decomposition of the sodium salts of the two bases occurs 

 when placed in urine or in meat extract. 



For illustrations of the sodium compounds of the two bases see 

 Virchow's Archives, 125, 556. 



The potassium compounds of heteroxanthin and paraxanthin are 

 well crystallized bodies, of high melting-point, and are more soluble 

 than the sodium compound. Their decompositions are the same as 

 those of the sodium salt. 



The reaction with sodium is the basis for Salomon's method of 

 recognition of these bases in small quantities of urine. The other 

 two mono-methyl derivatives form soluble sodium compounds. 



It can thus be distinguished from paraxanthin, the sodium com- 

 pound of which, on similar treatment, yields the characteristic crys- 

 talline form of the free base. This sodium reaction, therefore, 

 distinguishes it at once from xanthin, hypoxanthin, guanin, and 

 paraxanthin. It differs from the latter, as has already been indicated, 

 in the solubility and amorphous character of the free base ; in the 

 behavior of the hydrochlorid and the sodium compound, and in not 

 giving a precipitate with picric acid, nor the characteristic odor given 

 by paraxanthin on heating. 



The physiological action of heteroxanthin has been studied by 

 Kriiger and Salomon (1895). Its action is almost the same as that 

 of paraxanthin (page 403), indicating a close chemical relation. Its 

 action, however, is much less intense. A dose two or three times 

 greater than that of paraxanthin must be injected into frogs to pro- 

 duce the same symptoms. It has a local action producing early con- 

 traction and rigor of the muscles. Its general action is seen in the 

 gradual or rapid paralysis of respiration, according to the dose ; in 

 the loss of motion in the extremities, and in the decrease of re- 

 flexes. It is not as marked a diuretic as 3-methyl xanthin (pages 

 345, 397). 



Paraxanthin or 1-7-dimetliyl xanthin (p. 339), C^HgNPj, was 

 first isolated from urine by Thudichum (1879), who named it uro- 

 the'obromin. It was again isolated in 1883 by Salomon, who has 

 since shown it to be a constituent of normal urine, although present 

 in exceedingly minute quantity. Thus from 1,200 liters of urine 

 only 1.2 grams (0.0001 per cent.) of this substance were obtained. 

 From 10,000 liters of urine the yield was only 15.31 g., or less than 

 the amount of heteroxanthin (p. 389). It was also isolated in 1893 

 by Balke. 



The first synthesis of paraxanthin was effected by Fischer,^ who 

 ^Berichte, 30, 2408; 31, 2622. 



