906 APPENDIX. 



Guanin may, by the action of nitrous acid, be converted into xanthin. By 

 oxidation it can be made to yield principally guanidine and parabanic acid, accom- 

 panied, however, by small quantities of urea, xanthin, and oxalic acid. Capranica 

 has given several reactions characteristic of this body. 1 



Its separation from hypoxanthin and xanthin depends on its insolubility in 

 water and behavior with hydrochloric acid. 



Kynurenic acid. C 20 H 14 N 2 6 +2H 2 0. 



Found in the urine of dogs, and first described by Liebig. 2 When pure it crys- 

 tallizes in brilliant white needles, insoluble in cold, soluble in hot alcohol. The only 

 salt of this body which crystallizes well is that formed with barium. t\>r prepara- 

 tion and other particulars see Liebig, 3 Schultzen, and Schmiedeberg. 4 



Glycin. C 2 H 2 (NH 2 )0(OH). Also called Glycocol and Glycocin. 



Does not occur in a free state in the human body, but enters into the composi- 

 tion of many important substances, e. g. , hippuric and bile acids. It crystallizes 

 into large, colorless, hard rhombohedra, which are easily soluble in water, insoluble 

 in cold, slightly soluble in hot alcohol, insoluble in ether. It possesses an acid reac- 

 tion, but a sweet taste. It has also the property of uniting with both acids and 

 bases to form crystallizable compounds. In this it exhibits its amide nature, and 

 that it is an amide is rendered evident from the methods of its synthetic prepara- 

 tion ; thus mono-chloracetic acid and ammonia give glycin and anmionic chloride ; 

 C3H3C1.0 2 + 2NH 3 = C 2 H 2 (NH 2 )0(OH) + NH 4 C1. It is amido-acetic acid. 

 Heated with caustic baryta it yields ammonia and methylamine. 



Preparation. From glutin by the action of acids or alkalies ; from hippuric 

 acid by decomposing it with hydrochloric acid at a boiling temperature and remov- 

 ing by precipitation the simultaneously formed benzoic acid. 



Taurin. C 2 H 7 N0 3 S. 



In addition to entering into the composition of taurocholic acid taurin is found 

 in traces in the juices of muscle and in the lungs. 



It crystallizes in colorless, regular six-sided prisms [Fig. 251] ; these are readily 

 soluble in water, less so in alcohol. The solutions are neutral, It is a very stable 



r'Fio. 251. 



Taurin Crystals.] 



compound, resisting temperatures of less than 240 C. ; it is not acted on by dilute 

 alkalies and acids, even when boiled with them. It is not precipitated by metallic 



Taurin is amido-isethionic acid; and may be synthetically prepared from isethi- 

 onic (ethyl-sulphuric) acid by the action of ammonia ; thus : 



4 + NH 3 = S0 3 +H 2 0. 



1 Zeitschr. f. phys. Chem., Bd. iv. (1880), S. 240. 



2 Ann. d. Chem. u. Pharm., Bd. Ixxxvi. S. 125, and Bd. cviii., S. 354. 



3 Op. cit. * Ami. d. Chem. u. Pharm., Bd. clxiv. S. 155. 



