THE CHEMISTRY OF THE ANIMAL BODY. 997 



position product of nuclein. Combined with calcium it gives the brilliant 

 iridescence to fish-scales. 1 It is found in the fresher layers of deposited guano, 

 according to Voit being very probably derived from the fish eaten by the 

 water-fowl. 



(c) URIC ACIDS. 

 NH C - O 



Uric Acid, O = C C NH 



|| >CO. This acid is found in the nor- 



NH C NH 



mal urine in small amounts, and may be detected in the blood and tissues, 

 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 O 3 + 3NH 3 + 2H 2 O. 

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

 CC1 3 CHOH.CO.NH 2 + 2CO(NH 2 ) 2 = C 5 H 4 N 4 O 3 + 3HC1 + NH 3 + H 2 O. 



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. 966.) Presence of urea adds to its solubility. 2 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 = OCK^g ~ c8 



Alloxan. 



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



NH COv /NH CO 



>CO + = OC I + C0 2 . 



NH CO/ NOT CO 



Parabanic acid. 



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



KNH C = O /NH 2 



T + H 2 = OC< 

 NH c = o NNTH. co. coon 



Oxaluric acid. 



(4) And still another molecule of water added produces oxalic acid and urea : 3 



/NH 2 COOH 



OC< -f H 2 = I + OC(NH,) 2 . 



\NH.CO.COOH (X)OH 



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 and 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. 



1 Voit : Zeitschrift fur wissenschaftliche Zoologie, Bd. 15, p. 515. 



2 G. Kiidel : Archiv filr exper. Pathologic und Pharmakologie, 1893, Bd. 30, p. 469. 



3 See Bunge : Physiologische Chemie, 1894, p. 312. 



