270 Chemistry. [Lecture 33. 



tile; for, by mixing quick-lime with the resi- 

 duum, it will separate the volatile alkali in a 

 caustic state. 



The muriatic acid is easily discoverable by 

 mixture : we have in the nitrate of silver as nice 

 a test of this acid, as we have of the sulphuric 

 in the solution of lead. For this purpose it is 

 necessary that the nitrate of silver should contain 

 a little redundant acid, for if it is quite saturated, 

 it may be precipitated by an alkali or an earth ; 

 J)iit if there is a little more nitric acid than is 

 necessary to dissolve the silver, nothing will pre- 

 cipitate it but the muriatic acid, and it is sure to 

 do it in whatever state it is contained in the 

 mineral water. The nitrate cf silver has been 

 mentioned as a test of the presence of the sul- 

 phuric acid ; but I am convinced that it is not 

 affected by a small quantity of this acid, unless 

 it is united with the muriatic; for the sulphuric 

 acid composes with the silver a salt capable of 

 solution in water, whereas the compound with the 

 muriatic acid is totally incapable of solution. 



Earths are most commonly combined with the 

 sulphuric acid in a selenitic compound, which 

 in some measure is soluble in water. The proper 

 method of discovering lime, magnesia, or the 

 earth of alum, in water, is the addition of a car- 

 bonated alkali, which with the assistance of heat 

 precipitates the earth. Without heat we are not 

 .certain of separating the acid, and the mixture 

 must be kept warm for some time, or else the 



