XANTHIN. 391 



demonstrated in 1895 when Fischer effected the synthesis of caffein 

 (trimethyl xanthin) from dimethyl nric acid ; also, the conversion of 

 theobromin into the same uric acid derivative. 



Xanthin can be obtained most conveniently hj the action of 

 nitrous acid on guanin. The change may be represented by this 

 equation : 



C,H,Np + HNO, = C,H,N,0, + N, + H^. 



GUAinS. XUfTHIH. 



This reaction, first described by Strecker (1858), and later by 

 Fischer,* corresponds exactly to the one by which Kossel transformed 

 adenin into hypoxanthin (see page 353). 



By putrefaction guanin is also changed into xanthin, probably be- 

 cause of the action of the nitrous acid elaborated by bacteria (p. 367). 



Gautier, starting out on the hypothesis that xanthin is a polymeri- 

 zation product of hydrocyanic acid, endeavored to prepare it directly 

 &om this compound. Indeed, he claimed to have succeeded in 

 effecting the synthesis of not only xanthin, but also of its homo- 

 logue, by simply heating hydrocyanic acid in a sealed tube with 

 water and a little acetic acid, the latter being added to neutralize 

 any ammonia that might form. He expressed the reaction as fol- 

 lows : 



IIHCN + 4H,0 = C,H,Np, -|- Q^^fi^ + SNH, . 



XaHTHIM. MeTHTI. XiStTHIN. 



Fischer ' on repeating this experiment failed to obtain xanthin and 

 since then Grautier has not demonstrated the correctness of his 

 former view. 



Xanthin is a white, granular, amorphous body, and is deposited 

 from hot aqueous solution on cooling in colorless floccules, or as a 

 fine powder, which under the microscope is seen to consist of rounded 

 granules. According to Horbaczewski^ it can be easily obtained in 

 the crystalline form by adding acetic acid to an alkaline solution of 

 the base after previously diluting with hot water till the solution is 

 about 1 to 2000. The clear liquid, filtered if necessary, yields in a 

 few days a deposit upon the sides and bottom of the dish of groups 

 of crystals. These are thin, large, glistening, rhombic plates. If the 

 material is impure leucin-like balls or whetstone-shaped crystals 

 may form. The crystals contain one molecule of water, which is 

 not lost at 110°, but is given off at 125°- 130°. The synthetic 

 xanthin forms a colorless crystalline powder (Fischer). 



When occurring in calculi, it forms compact, moderately hard yel- 

 low, or brown fragments which on being rubbed with the finger- 

 nail, assume a wax-like appearance ; when isolated from the urine 



^Ann. d. Ghem., 215, 309. 



'Berichte, 30, 3131; 31, 449. 



' ZeU. physiol. Ghem., 23, 226 (1897). 



