Metals. 235 



as corrosive as the acids themselves ; d some 

 even more active, especially when taken into the 

 stomach. Ten or twelve drops of a mineral 

 acid diluted with water may be safely taken ; but 

 when combined with some of the metals, such a 

 dose produces the most dangerous effects. 



Metals, we have seen, may be separated from 

 the acids by one another; and it is worthy of 

 notice, that when one metal is employed to pre- 

 cipitate another, the metal which is the precipi- 

 tant dissolves without much effervescence, and 

 this becomes a salt, while the first metal is pre- 

 cipitated in its metallic state. This you will 

 easily understand if you attend to what has been 

 advanced ; for the acid with its oxygen is simply 

 transferred from one metal to the other; the 

 latter, therefore, remains dissolved by the liquor, 

 while the former sinks to the bottom. 



Alkalies in general precipitate the metals when 

 dissolved in the acids; yet, in many cases, if a 

 greater quantity than is necessary for precipi- 

 tating the metal is added to the mixture, it re- 

 dissolves the metal. The precipitation made by 

 the alkali is, however, not in the metallic form ; 

 and the reason is, that the alkali does not, like 

 a metal, attract the oxygen from the precipitate, 

 which therefore falls to the bottom in an oxid- 

 ized state. The oxide thus precipitated is 

 always heavier than the metal would have been 

 by oxidizement in the fire. The alkali also di 



