Chemical Effects of Caloric , fyc. 81 



confined to liquids ; many solids are also sus- 

 ceptible of it without previously passing through 

 the fluid state, of which camphor and carbonate 

 of ammonia are familiar examples. These very 

 substances, however, as well as others which have 

 been supposed incapable of liquefaction from 

 their volatility, are, in the common processes for 

 purifying them, reduced to the liquid state, and 

 even made to boil in vessels freely communi- 

 cating with the external air. 



Hence may be understood the nature of seve- 

 ral chemical operations, as evaporation, distilla- 

 tion, and sublimation. These processes are per- 

 formed on bodies composed of different ingre- 

 dients, some of which are more easily volatilized 

 than others. The most volatile will be first con- 

 verted into vapour. If we take a mass of clay, 

 water, and quicksilver, and expose this mass to 

 heat, the water will first rise in vapour, and be 

 entirely expelled before the mercury begins to 

 rise, and this vapour may be condensed into 

 pure water. By increasing the heat, the quick- 

 silver will rise also, and leave the clay by itself. 

 The process is called evaporation, and is used 

 when we wish to obtain the more fixed parts, 

 and are not solicitous about the volatile as in 

 the making of salt. When the volatile parts 

 are the object, the process is called either distil- 

 lation or sublimation , the former when the va- 

 pours condense into fluids, the latter into solids. 

 The product of sublimation is called sublimate^ 



5 



