116 HOW CROPS GROW. 



Hydrated Sulphuric Acid, 8ym. II 2 O SO 3 or H 2 SO 4 , 



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 acid 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 

 aeid, 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. 51. Placein a thin glass vessel, as a beaker glass, 30 c. 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 teaspoouful 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- 



