Identification of Organic Compounds. 19 



employed, and the adjoined figure (Fig. 4) illustrates an 

 apparatus employed for this purpose. This particular 

 form was employed by Professor Emil Fischer for separat- 

 ing derivatives of protein degradation products, to which 

 more detailed reference will be made later. In this case 

 it was found necessary to distil under very low pressures 

 (0*5 mm. of mercury or even less) to avoid decomposition. 

 The liquid to be distilled is placed in the flask a, with a 

 special form of side tube containing the thermometer, and 

 the various fractions are connected in receivers, one of 



Fig. 4 



which, d, is illustrated. The triangular glass-piece with 

 taps, c, is so devised that the receiver d can be opened 

 to the air and disconnected from the remainder of the 

 apparatus without interrupting appreciably the course of 

 the distillation ; a new receiver for collecting a different 

 fraction can then be put in its place. The lower vacuum 

 required is maintained by a power-driven double Geryk 

 pump, between which and the distillation apparatus a 

 receiver, e, cooled with liquid air, g, in a Dewar flask, /, 

 is interposed to prevent any vapours entering the pump. 



