DISTILLATION. 97 



Why is there ECONOMY IN EVAPORATION. It fol- 



no economy in lows that evaporation at low temperatures. 



evaporating at . 



low tempera- such as is practiced sometimes in sugar- 

 houses, has no advantage of economy. 

 The vapor that passes off, carries with it less sensible 

 heat, but enough more latent heat in proportion, to make 

 up the difference. 



235. DISTILLATION. Distillation con- 



Descnoe the 



process <>/ dis- sists in converting a liquid into vapor, and 

 recondensing the vapor. The apparatus 

 represented in the figure, 

 suffices for illustration. 

 Water being boiled in the 

 test-tube, the steam con- 

 denses in the cooler vial. 

 If the latter be covered 

 with wet paper, the con- "~ 

 densation is more perfect. The apparatus commonly 

 used in distillation, consisting of retort and receiver, is 

 represented in the appendix. 



236. OBJECT OF DISTILLATION. The ob- 

 object*} *&%> J ect f distillation is commonly to purify, 

 tiilationf O r, in other words, to separate the liquid 

 distilled, from other substances with which 

 it may be mixed. Thus, sea water is distilled to sepa- 

 rate the pure water from salt. The water becomes 

 steam, and is condensed as pure water, while the salt 

 remains behind. So alcohol is distilled, or converted 

 into vapor, and recondensed, to separate it from water, 

 and the various refuse matters which are mixed with 

 it after fermentation. But the separation is not per- 



5 



