122. Mr. Kirwan’s Experiments 
The marine acid is the beft adapted to the production of 
hepatic air. If the concentrated nitrous acid be ufed, it will 
afford nitrous air; but having diluted fome nitrous acid, whofa 
fpecific gravity was 1,347, with 20 times its bulk of water, I 
obtained, with the affiftance of heat, as pure hepatic air as 
with any other acid. 
The concentrated vitriolic acid, poured on liver of fulphur, 
affords but little hepatic air without the affiftance of heat, 
though it iilftantly decompofes the liver of fulphur ; and it is 
partly for this reafon that the proportion of air is fo fmall ; for 
it is during the gradual decompofition of fulphureous com- 
pounds that hepatic air is produced. 
Diftilled vinegar extricates this air in the temperature of the 
atmofphere ; but it is not pure, its peculiar fmell being mixed 
with that of vinegar. 
The acid of fugar alfo produced fome quantity of this air in 
the temperature of 59 0 . 
20 grains of fe dative fait , or acid (as it fhould more properly 
be called) diflolved in an ounce of water, being poured on liver 
of fulphur, afforded hepatic air only when in a boiling heat, 
or nearly fo. 
Neither the aerial nor arfenical acids produce any. 
Liver of fulphur is foluble not only in water but in fpirit of 
wine, and in cauftic volatile alkalies ; and the colour of both 
folutions is red. Sulphur is precipitable from the former by 
the addition of water or of an acid, but from the latter only 
by an acid. 
Having made fome liver of fulphur* in which the pro- 
portion of fulphur much exceeded that of the alkali, I 
poured on part of it fame oil of vitriol, whofe fpecific gravity 
was 1,863; by this means I obtained hepatic air, fo loaded 
with 
