328 DISTILLATION. 



must be kept cool. This is done by constantly feeding it 

 at the bottom with cold water, as explained in the last 

 article. 



(a. ) Fig. 252 represents a simpler form of apparatus for this pur- 

 pose. The retort is a Florence flask, the delivery tube of which 

 passes through a "water-jacket." The method of supplying this 

 condenser with cold water is evident from the figure. Sometimes 

 the delivery tube passes directly into a vessel placed in a cold water 

 bath, this vessel serving as both condenser and receiver. 



513. Distillation of a Liquid from a Liquid. 



Suppose that alcohol is to be separated from water. 

 The solution is placed in the retort and heated to about 

 90 C., which is above the boiling point of alcohol but 

 below that of water. The alcohol will pass over in a state 

 of vapor and be condensed, while the water, etc., remains 

 behind. In practice, the alcohol vapor passes over charged 

 with a certain amount of steam. A receiver placed in a 

 bath containing boiling water is interposed between the 

 retort and the worm or condenser. In this receiver the 

 steam condenses, while the vapor of alcohol passes on to 

 the worm where it also is condensed. This process is known 

 as "fractional distillation.' 5 



Recapitulation. In this section we have considered 

 the meaning of Liquefaction ; the Laws of Fu- 

 sion ; the meaning and kinds of Vaporization ; 

 Evaporation in air and in vacuo ; Ebullition and 

 its Laws; effect of Pressure upon the boiling point; 

 Steam ; definition of Boiling Point ; Distilla- 

 tion. 



