Identification of Organic Compounds. 17 



a thermometer is inserted in the neck so that the reservoir 

 is just level with the side tube, which is then connected 

 with one end of a condensing tube, placed at such an 

 angle that the liquid, after vaporizing and condensing, 

 readily flows out at the other. In the case of liquids of 

 low boiling point, it is necessary to surround the condens- 

 ing tube with an outer tube, through which a stream of 

 cold water continuously circulates ; * but with less volatile 



substances (substances with higher boiling points) this is 

 unnecessary, and a simple "air condenser" is sufficient. 

 If, now, the liquid in the fractionating flask is heated, a 

 point may be reached at which it will boil, and the vapour 

 will condense and flow out through the lower end of the 

 condensing tube, and may be collected in a suitable vessel 

 used as a receiver. When a pure liquid is being distilled 

 in this way, the thermometer will indicate a constant 



* Various forms of condensers, some with "double surface" condensing 

 systems, will be found in the catalogues of apparatus manufacturers. 

 (1,997) 2 



