OF AGRICULTURE. 229 



sensation. It has a powerful affinity for water ; when 

 a splinter of wood is dropped into it for a short time 

 it "chars" or turns black, the acid decomposing it 

 into water and carbon. In like manner it decom- 

 poses the skin, and most organic substances, by 

 removing their water. It is an active poison, the 

 best antidote being copious draughts of water and 

 chalk, or the carbonate of soda or magnesia. 



Uses. Sulphuric acid is extensively used in the 

 manufacture of soda from common salt; also in the 

 manufacture of chlorine for bleaching; of citric, 

 tartaric, acetic, nitric and muriatic acids, sulphate of 

 soda, sulphate of magnesia; also dyeing, calico print- 

 ing, gold and silver refining, and in purifying oils 

 and tallow. Its chemical uses are innumerable. It 

 is the Hercules of the acids. Its uses in agriculture 

 have been before stated. 



This acid unites with bases forming the sulphates, 

 and exists in nature both combined, as with lime in 

 sulphate of lime, or gypsum, and free, as in some 

 streams of water and springs, the water of which it 

 renders acid. It is nearly twice as heavy as water, a 

 gallon weighing thirteen pounds. The test for sul- 

 phuric acid is the chloride of barium, with which it 

 forms an insolube precipitate. 



Phosphoric Acid. Phosphorus has an intense affinity 

 for oxygen. Place a bit of phosphorus, of the size of a 

 pea, in a wine glass; cover it with hot water, and 

 direct against it a current of oxygen gas, it will burst 

 into violent combustion beneath the surface of the 

 water. When a match is burned, the white smoke 

 that appears is phosphoric acid ; it is always produced 

 when phosphorus is burned in dry air or oxygen gas. 



