On Sal Nitrum and Nitro- Aerial Spirit i6i 



will be coagulated with the fixed salt of tartar, but the 

 volatile salt, of which it also in part consists, ascends 

 of the same nature as before. And the reason of this 

 is, that the acid spirit of salt is capable of entering 

 into closer union with any fixed salt than it is with 

 a volatile salt, so that it immediately leaves the volatile 

 salts that it may be combined more intimately with 

 the fixed salt. But if oil of vitriol is united with salt of 

 tartar, they can scarcely be separated from each other. 

 And yet this is not because these salts have mutually 

 destroyed each other, but because there is nothing in 

 nature with which either of them can unite more 

 firmly than they do with each other. 



As acid salts leave volatile salts to form a closer 

 union with the fixed salt of tartar, as being a more 

 suitable partner, so doubtless fixed salts select some 

 one acid in preference to others that they may com- 

 bine with it in a closer union. 



But to illustrate this by an example : if oil of vitriol 

 is poured upon nitre, which consists of an alkaline 

 and of a volatile acid salt (as was shown above), the 

 fixed salt of the nitre will soon leave its own acid and 

 will enter into union with the acid of the vitriol, which 

 is more concordant with it ; so that nitrous acid, 

 on account of the mixture with the vitriolic acid, is 

 correctly said to be precipitated from the embraces of 

 the alkaline salt. That the case is so, is clear, for 

 if nitre mixed with oil of vitriol be distilled, the 

 spirit or acid salt of the nitre will pass under a mild 

 heat into the receiving vessel, while yet in other 

 circumstances that spirit will not be carried up except 

 by a very vehement fire. No doubt it is because the 

 volatile acid salt of the nitre has been expelled from 

 the society of the alkaline salt by the more fixed 

 vitriolic acid that the acid of nitre, now liberated from 



L 



