Concentrating Chamber Acid to Oil of Vitriol: Lead Pans, Then Glass

The lead chamber makes a weak acid. To get oil of vitriol, the strong acid of trade, the water is boiled off: first in shallow pans of sheet lead, then, once the acid is strong enough to attack lead, in glass retorts on a sand-bath. This is the British works practice Andrew Ure described in 1839. The finished acid has a specific gravity of about 1.84, which is about 98 % acid.