166 METALLOIDS. 



Even the dilute acid acts on all the metals hereafter 

 named, as far as manganese. 



400. The action of the dilute acid may 



Illustrate the . . 



action of the be illustrated, by placing a few bits of zinc 

 dilute acid. in a tumbler? with a i itt i e waterj an d ad- 

 ding a small portion of oil of vitriol. The metal dis- 

 solves with the evolution of hydrogen gas. The rea- 

 son of the evolution of this gas has been already 

 given. 



401. The action of the strong acid may 



Illustrate the J 



action of the be illustrated, by heating a little copper, 

 strong acid. w{ih Q[{ of vitriol> in a test-tube. The 



metal dissolves with the evolution of sulphurous acid 

 fumes. The reason of the appearance of sulphurous 

 acid will be given in the next section. 



402. AFFINITY FOR WATER. The affin- 

 liffinlt *ofwl- ity f sulphuric acid for water is so strong 

 phurtc add that it lays hold on every particle of the 



for water? . / f , 



invisible aqueous vapor of the atmosphere. 

 It finds it, in what seems the driest air ; and every par- 

 ticle which it catches, it retains. It grows in bulk 

 by what it thus drinks, as will be seen if a little oil of 

 vitriol is left exposed to the air, for a few days, in an 

 open vessel. It is sometimes necessary, in chemical 

 operations, to free gases from all the aqueous vapor 

 which is mixed with them. This is done completely, 

 by causing them to bubble through oil of vitriol, and 

 again collecting them. 



403. HEAT BY DILUTION. When sul- 



What takes . 



place whensui- phuric acid and water are mixed, conden- 

 U sat i n ta ^ es place, accompanied by eleva- 

 tion of temperature. Fiftv cubic inches of 



