ACIDS. 
411 
sulphuric acid, containing twelve hundred parts of oxygen. 
Besides, after the combustion of the sulphur, the residuary 
salts contain nearly as much oxygen as was originally con 
tained in the nitre ; and twelve hundred parts of oxygen in 
the acid could not be accounted for. 
Pluvinet first attempted to explain this circumstance, in a 
letter to the elder Chaptal, and since then, Messrs. Clement 
and Desormes, two French manufacturing chemists, have 
revived, after a lapse of some years, this theory, and their 
explanation has since been received as true, by Mr. Dalton 
and Sir H. Davy. It is now supposed, that the burning sul 
phur, taking from the nitre a portion of its oxygen, forms 
sulphuric acid, which, uniting with the base of the nitre, 
or potasse, displaces nitric and nitrous acids in vapour, 
which is decomposed by the sulphurous gas, into nitrous 
gas, or deutoxide of azote. Being naturally only a little 
heavier than air, and being then rarefied by the heat, the 
nitrous gas rises to the roof of the chamber, and there 
coming into contact with atmospheric air, by means of 
a hole left there for that purpose, and without which, as 
they affirm, the manufacturers found that the acidification 
would not go on, forms nitrous acid vapour, which being a 
heavy body, immediately precipitates on the sulphurous 
flames. Sulphuric acid and nitrous gas are again formed, 
and the latter again mounts for a new charge of oxygen, 
again to re-descend and transfer it to the sulphur. 
Sir H. Davy has, however, since shewn, that water is ne 
cessary to the mutual action of sulphurous gas and nitrous 
gas, and unless this fluid is present the process does not go 
on. With this additional fact it would appear, that a small 
volume of nitrous acid vapour, by its alternate and frequent 
changes into oxide and acid, is capable of acidifying a great 
quantity of sulphur. 
A manufacturer of this acid remarks, in the “ Chemist,' 
that the method described by Parkes has been abandoned 
by the English makers. It proves, however, though Messrs. 
Clement and Desormes affirm the contrary, that the acidifi 
cation will go on without any hole, for the admission of at 
mospheric air, in the roof of the chamber. In the old method 
of operating, the first charge, by being burnt, would form 
some portion of incondensible gas ; this, by the admission of 
atmospheric air at the doors, was driven to the top, and thus 
cach charge lessened the capacity of the chamber, until, after 
a week’s work, the sulphur would scarcelyinflame. Ona mo 
derate computation, notone half ofthe sulphur was really used.