PREPARATION OF PURE COMPOUNDS 



ii 



Fig. 6: the apparatus can be rotated on the cork connecting it with the 

 distilling flask when a new fraction begins to distil over. 



FIG. 5. FIG. 6. 



An apparatus of the type in Fig. 7 is the most convenient. By means of 

 the several taps the receiver can be shut off and its vacuum released, whilst 

 distillation continues and the fraction collects in the bulb. The fresh 



FIG. 



receiver is exhausted whilst the taps to the bulb and distilling flasks are 

 closed; no great decrease of vacuum occurs as the small receivers are 

 rapidly exhausted. 



If necessary the bulb and receiver can be cooled by a stream of cold water, 

 or by immersing the receiver in ice or a freezing mixture. 



