32 
ON AQUA-REGIA. 
ART. VI. — ON AQUA-REGIA. 
By M. Gay-Lussac. 
Since the time of Berthollet, most chemists have con- 
sidered aqua-regia, or the mixture of nitric and hydrochlo- 
ric acids in variable proportions, as composed of free chlo- 
rine and nitrous gas, held in solution by the two acids, and 
more particularly by the nitric acid. Berthollet also showed 
that chlorine and nitrous gas combine at the moment of 
mixture, and are subject to a considerable condensation of 
volume. After 50 years of silence upon this point, Edmond 
Davy discovered that when nitric is allowed to act upon 
common salt, a gaseous mixture is evolved of an orange- 
yellow colour, which contains chlorine, and another gas 
easily absorbable by water. He likewise pointed out the 
similarity of this gaseous mixture to the condensible com- 
pound of chlorine and nitrous gas of Berthollet, and was led 
by his experiments to the conclusion that the gas was com- 
posed of equal volumes of chlorine and nitrous gas, united 
without condensation. Baudrimont here took up the inves- 
tigation, and condensed into a reddish-brown liquid, by 
means of a freezing mixture, the gas evolved from aqua-re- 
gia. His analysis of the compound induced him to assign 
it the formula — 
» .. ' no 3 ci 2 . -.. : m 
and to substitute the name of chloronitric acid'in the place 
of chloronitrous acid, given to it by Davy. This compound 
was considered by Baudrimont as the active principle of 
aqua-regia. Notwithstanding these experiments, the majo- 
rity were still in the habit of viewing aqua-regia, with Ber- 
zelius, in the same light as it was viewed by Berthollet. 
The composition of M. Baudrimont's compound, and the 
