116 HOW CROPS GROW. 
Hydrated Sulphuric Acid, Sym. H, O SO, or H, SO,, 
mo. wt. 98—the sulphuric acid of commerce—is a substance 
of the highest importance, its manufacture being the basis 
of the chemical arts. In its concentrated form it is known 
as oil of vitriol, and is a colorless, heavy liquid, of an 
oily consistency, and sharp, sour taste. 
It is manufactured on the large scale by mingling sul- 
phurous acid gas, nitric acid gas, and steam, in large lead- 
lined chambers, the floors of which are covered with wa- 
ter. The sulphurous acid takes up oxygen from the nitric 
acid, and the sulphuric acid thus formed dissolves in the 
water, and is afterwards boiled down to the proper strength 
in glass vessels, 
The chief agricultural application of commercial sul- 
phuric acid is in the preparation of “superphosphate of 
lime,” which is consumed as a fertilizer in immense quan- 
tities. This is made by mixing together dilute sulphuric 
acid with bone-dust, bone-ash, or some mineral phosphate. 
Sulphuric acid occurs in the free state, though extreme- 
ly dilute, in certain natural waters, as in the Oak Orchard 
Acid Spring of Orleans, N. Y., where it is produced by 
the ‘oxidation of sulphide of iron. 
Sulphuric adid is very corrosive and destructive to most 
vegetable and animal matters. 
Exp. 53.—Stir a little oil of vitriol with a pine stick. The wood is 
immediately browned or blackened, and a portion of it dissolves in the 
acid, communicating a dark color to the latter. The commercial acid is 
often brown from contact with straws and chips. 
Strong sulphuric acid produces great heat when mixed with water, as 
is done for making superphosphate. 
Exp. 54.—Place in a thin glass vessel, as a beaker glass, 30 ¢. c. of wa- 
ter; into this pour in a fine stream 120 grams of oil of vitriol, stirring 
all-the while with a narrow test tube, containing a teaspoonful of water, 
If the acid be of full strength, so much heat is thus generated as to boil 
the water in the stirring tube. 
In mixing oil of vitriol and water, the acid should always be slowly 
poured into the water, with stirring, as above directed. When water is 
added to the acid, it floats upon the latter, or mixes with it but super- 
