VIII. ACIDS.— Sulphuric 309 



chamber. Evaporate this acid in leaden pans to sp. gr. 1-532 or 

 50 deg. Baume; then distil it in glass retorts, or a platina still 

 with a leaden head, until all the water has come over, and the acid 

 is brought to sp. gr. I'S^o or 66 deg. Baume, so that a bottle 

 holding 12 oz. of water should hold full 22 oz. of this acid; the 

 produce is from 2500 to 26001 b. of acid. 



2. Upon an iron dish set on a furnace, and communicating with 

 a leaden chamber 50 feet long, 27 wide, and 15 high, the bottom 

 of which is covered with a sheet of sulphuric acid, sp. gr. 1*075 

 or 10 deg. Baume, throw lOOlb. of rough brimstone, which 

 should take fire immediately: at the same time the vapour from 

 the mixture of lib. of treacle and 91b. of smoking nitrous acid, 

 heated in a bolt head, set on the sand bath of an adjoining fur- 

 Dace, is admitted about two feet above the burning sulphur. In 

 two hours'* time the steam of 10 gallons of water is to be admitted, 

 and a small hole opened just above the burning brimstone to admit 

 the air. "When the steam is condensed, the door by which the 

 brimstone was introduced, and two chimneys at the further end of 

 the chamber, are opened to renew the air in the chamber for a 

 fresh operation. Four operations may be made in 24 hours, but 

 it is preferable to perform only three, or even two. The acid 

 drawn off is about sp. gr. 1*381. or 40 deg. Baume ; if less steam 

 is injected and the sp. gr. raised to 1-532 or 50 deg. Baume, it 

 absorbs some of the nitrous gas, which cannot afterwards be sepa- 

 rated from it, and which renders it unfit for making the solution 

 of indigo used by the dyers. The acid thus obtained is then con- 

 centrated as before. This produces 300lb. of acid, sp. gr. 1*845 

 or 6(5 deg. Baume, from each lOOlb. of brimstone, which is only 

 121b. less than the theoretical product. The abstraction of the 

 nitric acid from the treacle produces oxalic acid, which saves the 

 whole expense of the saltpetre. 



HilTs patmt oil of vitriol The native sulphuret of iron, or 

 martial pyrites, is distilled, and an imponderable substance, as the 

 patent terms it, is to be injected into the chamber ; this may be 

 oxygen gas from black oxide of manganese. 



Henry s ffulphuric acid for assays. Rectified oil of vitriol diluted 

 to sn. gr. 1-135 : it has the same power of saturation as his nitric 

 Acicl and muriatic acid. 



Rectified oil of vitriol. Oleum vitrioli rectificatnm. Distil, in a 

 sand pot, oil of vitriol 4 oz. at a time in a large green-glass retort 

 into an unlutcd receiver, fitting very loosely to the retort. Dr. 

 Bryan Higgins observed, that green glass was apt to crack, and 

 that even Hint glass retorts would crack if the sand rose up higher 

 tiian the evaporable charge. Dr. Urc says, he can distil a pint or 

 nearly 21b. of acid in a continuous stream, without heating the 



