180 CHEMISTEY. 



agents of the chemist in his operations. " What iron is to 

 the machinist," says Stockhardt, "sulphuric acid is to the 

 chemist. It stands, as it were, the Hercules among the acids, 

 and by it we are able to overpower all others, and expel 

 them from their combinations." It chars most vegetable 



JD 



and animal substances. If a bit of wood be introduced 

 into it, it becomes black, and in fact is reduced to coal, as 

 if it had been burned ; for, being composed of carbon, oxy- 

 gen, and hydrogen, the sulphuric acid takes away the two 

 latter, combining them to form water, and leaves the car- 

 bon untouched. It does the same thing to sugar, as that is 

 composed of the same ingredients as wood. 



245. Development of Heat. If water and sulphuric acid 

 be mixed together, considerable heat is evolved by the 

 chemical union which takes place between them. This may 

 be shown very prettily by the following experiment : Put 

 some tow or cotton around a wine-glass, with some little 

 bits of phosphorus placed in it in such a way as to be in 

 contact with the glass. If now you pour into it some sul- 

 phuric acid, and then some water, the heat produced will 

 burn up the combustible material around the glass. It is 

 supposed that the heat is caused by a condensation which 

 takes place in the union of the acid and the water. If 50 

 measures of the acid are mixed with 50 of water, we do not 

 have as the result 100 measures of the mixture, but only 97, 

 showing a contraction or condensation which is considered 

 adequate to the production of the heat. 



246. A Practical Direction. The heat caused by the union 

 of water and sulphuric acid explains the reason of a practi- 

 cal direction that may be given in regard to an accident 

 which sometimes happens with sulphuric acid. If some of 

 the acid be spilled upon the skin, just wipe off as much of it 

 as you can with a piece of dry cloth or paper, and then use 

 a large quantity of water in washing off the rest, so that 



