THE CHEMISTRY OE THE ANIMAL BODY. 555 



especially in gout. It is the principal excrement of birds and snakes, that of 

 the latter being almost pure ammonium urate. 



Preparation. — (1) By heating glycocoll with urea at 200° : 



C 2 H 5 N0 2 + 3CO(NH 2 ) 2 == C 5 H 4 N 4 3 + 3NH 3 + 2H 2 0. 



(2) By heating the amide of trichlorlactic acid with urea : 



CCl 3 CHOH.CO.NH 2 + 2CO(NH 2 ) 2 - C 5 H 4 X 4 C) 3 + 3HC1 + NH 3 + H 2 0. 



Properties. — Uric acid may be deposited in white hard crystals, which are 

 tasteless, odorless, and almost insoluble in water, alcohol, or ether. (For its 

 solution in the urine see p. 522.) Preseuce of urea adds to its solubility. 1 Its 

 most soluble salts are those of lithium and piperazin. Uric acid is dibasic — 

 that is, two of its hydrogen atoms may be replaced by monad elements. 



(1) Nitric acid in the cold converts uric acid into urea and alloxan: 



C 5 H 4 N 4 3 + + H 2 = OC<^gZco> co + OC(NH 2 ) 2 . 



Alloxan. 



(2) Whereas, if the hot acid acts, it produces parabanic acid: 



/NH — CO\ /NH — CO 



OC< >CO + = OC< j +co 2 . 



\nh-cck \NH-eo 



Parabanic acid. 



(3) Through water addition parabanic acid becomes oxaluric acid: 



/NH — C = /NH 2 



OC< I + H,0 = OC< 



\NH-C = \NH.CO.COOH 



Oxaluric acid. 



(4) And still another molecule of water added produces oxalic acid and urea: ' 



/NH 2 COOH 



OC< +H 2 0=| +OC(NH 2 ) 2 . 



Nmco.cooH cooH 



Oxalic acid. 



The above reactions lead up to the constitutional formula of uric acid, and show its 

 decomposition into urea and oxalic acid through oxidation ami hydrolysis. It is known 

 that uric acid when fed increases the amount of urea in the urine, and it is possible that 

 the oxalic acid in the urine may have the same source. 



Uric acid oxidized with permanganate of potassium is converted into <il/<u<f<>ht, 



/NH— CH— NH\ 



OC< | >co. 



V\ll, co-Nil/ 



a substance which is found in the allantoic fluid, ami in the urine ofpregnanl women ami 

 of newborn children, and in the urine of dogs alter feeding thymus (see below). 



If uric acid be carefully evaporated with nitric acid on a small white porcelain cover, 

 a reddish residue remains, which moistened with ammonia gives a brilliant purple color, 

 due to the formation of murexid, C 8 H 4 (NH 4 )N 6 8 ; subsequent addition of alkali gives 

 a red coloration. This is known as the murexid test and is very delicate, 



The Purin Bases in the Body. — All true nucleins yield one or more of 



the purin bases. Nucleins are combinations of nucleic acid and proteid, 



' G. Riidel : Archiv fur exper. Pathologic un<l Ph<tmuik<>l<»jie, 1S93, lid. 30, S. 469. 

 3 See Bunge: Physiologische Chemie, L894, S. 312. 



