on treating Uric with Nitrous Acid, ec. 31 
variety of products must be obtained. This inference is parti- 
cularly confirmed, when it is exposed to the action of nitric or 
nitrous acid; and the phenomena which accompany this action 
are so singular, as to excite curiosity respecting the chemical al- 
terations which are its effects. 
Scheele, the celebrated discoverer of uric acid, first observed 
in like manner the violent action of nitrous acid on this sub- 
stance, and the red colour which its solution leaves on the skin, 
or which it acquires in evaporating; but by one drop of nitrous 
acid it is instantly destroyed. He likewise observed that this 
solution had always an acid taste, that it did not alter the me- 
tallic solutions, nor precipitate with muriate of barytes; but, on 
the other hand, it yielded in lime-water a white precipitate 
which was soluble in nitrous and muriatic acids without efferves- 
cence. 
Bergman observed, that when treated with potash in excess it 
did not become turbid, but by digestion acquired a reddish co- 
lour which readily tinged the skin, and the solution thus joined 
to potash precipitated in a particular manner the metallic solu- 
tions*. He also considered as very remarkable the fine red co- 
lour which he obtained by treating urie with nitrous acid, and 
examined the circumstances which accompanied the appearance 
of this colour, and its destruction effected by acids or caustic al- 
kali¢. ‘The same chemist and Scopoli afterwards observed that 
the reciprocal action of these acids produced a considerable 
quantity of oxalic acid { ; a change which my father found to be 
greater and more rapid, if, instead of nitrous acid, chlorine were 
used §. These observations directed Fourcroy to determine 
what were really the changes produced on uric acid by chlorine, 
which there was every reason to believe could not be very dis- 
similar from_those effected by nitric acid. He found that un- 
der water chlorine changed uric acid into ammonia and carbonie, 
oxalic and malic acids. The first acid formed is the malic, 
which with the continued action of the chlorine changes into 
oxalic; and this increasing, both acids are resolved into carbonic 
and water ||. These are the changes which chemists have hi- 
therto observed as taking place in uric acid when treated in this 
manner. To me, however, it appears that many others are pro- 
duced, as will be seen by the subsequent observations. When a 
little uric acid dissolved in nitrous acid is reduced to dryness, 
having a red colour, and exposed to the flame of a lamp ina 
* Scheele, Mem. de Chym. t. i. + Bergman, Opuse. t. iv. Ob- 
ser. de Cal. Urin. t Crell, dun. 178. Sce Brugnatelli’s Memoir 
on the Sediment of Urine, where the history of this discovery is related, 
p- 116. : § Ann. de Chimie, xxx. p. 133. || Fourcroy, Syst. des 
Jon. Chim. t. x. p. 222. 
watch- 
