On Sal Nitrtim and Nitro- Aerial Spirit 157 



sort, abounding in volatile sulphur, are quite in- 

 capable of dissolving fixed salts, so that neither can 

 the alkaline salt of quicklime be dissolved by them, 

 and yet this is an indispensable condition of the 

 production of heat in lime, as will be shown later. 

 So that it is abundantly clear that the heat of quick- 

 lime is not, as is commonly supposed, produced by the 

 igneous particles which are simply fixed in it, being 

 thrown, at last, into vigorous motion by the humidity 

 which is antagonistic to them, but by the liberation 

 and effervescence of its salts ; inasmuch as quicklime 

 does not become hot when moistened by any liquid 

 indiscriminately, but only by such as are fitted for 

 speedily dissolving its salts. Nay, the liquids which, 

 in consequence of abounding in volatile sulphur, are 

 best adapted to set igneous particles in motion and 

 produce heat, when poured on quicklime produce no 

 heat in it, although, on the other hand, the same lime 

 becomes very hot when sprinkled with aqueous fluids, 

 the chief extinguishers of fire and heat. But this can 

 result from no other cause than the fitness of the 

 latter, but not of the former, liquids to dissolve its 

 salts. 



It remains now to inquire whence these different 

 salts of lime trace their descent. In the first place, 

 then, with respect to the origin of the fixed salt, it is 

 generated in the same way as in earth. For as the 

 seeds of fixed salts lie hidden in the earth's bosom, as 

 was elsewhere shown, so too, they may be found in 

 shells, chalk, and stones ; and the-proof of this is that 

 most of these effervesce with any acid spirit poured 

 upon them. 



As regards the origin of the acid salt of quicklime, 

 we must believe that it is made by the action of 

 nitro-aerial and igneous particles during the long 



