413 
ACIDS. 
forms us that sulphuric acid was manufactured in France, 
forty years ago, by burning sulphur with saltpetre, but at 
present, by reverting to the old process of burning sulphur 
alone. 
The process with saltpetre consisted in shoving into a 
chamber lined with lead, containing from five to ten thou 
sand cubic feet, an iron carriage, carrying a cast-iron dish 
full of burning sulphur, the combustion of which was pro 
moted by a portion of saltpetre, amounting to ten, fifteen, 
or even twenty in the hundred. Some manufacturers in 
jected a shower of water by a forcing pump, through a rose. 
When it was supposed that the combustion was completed 
and that the acid formed had been condensed by the water, 
the door was opened at which the chariot had been intro 
duced, it was taken out to clear away.the residuum, again 
loaded, and the operation repeated. 
The acid obtained was evaporated’and concentrated in 
leaden boilers •50° to Baumé, and then concentrated in 
glass retorts, ranged, as many as twenty or thirty, in a sand 
bath, and all heated by the same fire. 
The result of all these proceedings was to obtain from 150 
to 200 parts of sulphuric acid, of the specific gravity of 1,845, 
or 66° of Baumé for every hundred of sulphur employed, 
and very often the operation entirely failed. The residuum 
was at first flung away, although it contained nearly one 
third of the sulphur used, and much sulphate of potasse ; 
but afterwards it was sold to the alum-works, and used in 
that manufactory. 
The putting in the sulphur by a carriage was then done 
away, and an immoveable furnace constructed under the 
chamber. The dish in which the sulphur was burnt was 
heated by fire, and the mixture of one hundred parts sul 
phur to ten or twelve saltpetre was introduced from time to 
time, by means of a small door for this purpose. A hole, 
two inches above the level of the sulphur, permitted a con 
stant ingress of air, and a chimney at the other extremity 
created a draught which carried off the uncondensed gases. 
In damp weather, particularly, they fell all around, and de 
stroyed all vegetation in a pretty extensive circle. 
Some acid was always left in the chamber ; and as more 
was formed, a quantity was drawn off and concentrated in 
glass vessels. This method of concentrating the acid is 
still generally employed, except that, instead of several glass 
retorts, a single platinum alembic is now in use. By this