URIC ACID. 
5§7 
residues on to a nucleus derived from lactic acid. This Horbaczewski 
succeeded in doing by heating urea, with trichorlactamide : — 
CCL 3 CH.OH.CO.NH 2 +2(NH 2 ) 2 CO=C 6 H 4 N 4 3 + XIT 4 C1 + 2HC1+KLO 
The simple changes involved in this reaction will be more clearly seen on 
examination of the following graphic scheme : — 
HNH 
1 
CI 
C1.C.C1 
HNH 
CO 
1 
CH(OH) 
HNH 
HNH 
(urea) 
COXHo 
(trichlorlactamide) 
(urea) 
\ 
CO 
The groups printed in thick type unite to form uric acid ; the atoms repre- 
sented in thinner type split off to form respectively a molecule of ammonium 
chloride, two molecules of hydrochloric acid, and one of water. 
Uric acid is formed also when glycine is heated with urea (Hor- 
baczewski), but the molecular changes involved are not so simple 
as those shown above, and the yield is not so good. In Behrend and 
Eoosen's synthesis the nucleus is primarily derived from acet-acetic 
ether, and the urea residues are linked on separately at two different 
stages in the synthetic process. 
Properties. — Pure uric acid forms a white powder, which is made up 
of small rhombic crystals, of more or less prismatic or tabular type. Its 
crystalline forms become very diverse in the presence of impurities, 
and when it separates from the urine, the crystals, which are then always 
coloured, take shapes which depend to a large extent upon the nature of 
the pigment associated with them 1 (Figs. 50 and 51). 
In cold water it is very in- 
soluble, only dissolving to the ex- 
tent of about 1 part in 15,000. 
A litre of boiling water takes 
up about half a gramme. Ether 
and alcohol do not dissolve it. It 
dissolves in oil of vitriol without 
decomposition, and from the solu- 
tion a crystalline sulphate separates 
on freezing the mixture. By this 
process pure uric acid may be 
obtained from contaminated speci- 
mens, the sulphate being resolved 
into its constituents when treated 
with water. 
It acts as a somewdiat weak 
dibasic acid, but forms three orders 
of salts. 
1. The neutral urates, M'.U, have an intense caustic taste and are 
very unstable. They are decomposed by carbonates and even by the 
carbonic acid of the air. As they are only produced in the presence of 
caustic alkalies, and cannot exist in the presence of carbonates, it is un- 
1 A. E. Garrod. 
Fig. 50. — Uric acid. 
