General Principles. 53 



mineral waters. It is not, however, to be ob- 

 tained in a simple state by any process, and the 

 purest is in that of carbonic acid gas, which 

 was formerly known by the names of fixed and 

 fixable air, from its uniting with chalk, lime, 

 magnesia, &c. in a solid form. It was also 

 called mephitic (or poisonous) air, from its de- 

 stroying life when inspired into the lungs ; and 

 was long known to miners under the name of 

 choak-damp. 



Carbonic acid, united with the alkalies, lime, 

 magnesia, and some other of the earths, reduces 

 them to the state of carbonats, neutralises them, 

 and deprives them of their caustic (or burning) 

 properties. I shall have to add more upon this 

 subject under the class of Acids. 



With the other simple combustibles, and 

 some other bodies, carbon unites, forming car- 

 burets. 



VIII. Of the MURIATIC radical little is to be 

 said, because it never has been found in an un- 

 combined state. It has not been yet obtained 

 even in the gaseous state uncombined with oxy- 

 gen, so strong is its attraction for that sub- 

 stance. In that form, however, the muriatic 

 acid is to be procured, and is termed muriatic 

 acid gas. 



Muriatic acid and black oxide of manganese 

 being heated, a gas is evolved, in which combus- 

 tible bodies burn with splendour, as in oxygen, 

 and with which they also form binary compounds : 





