74 



PROPERTIES OF CERTAIN AMINO-ACIDS. [CH. IV. 



(v.) When as much acid as possible has been removed, slowly 

 open the screw C to abolish the vacuum. Cautiously dis- 

 connect the rubber tubing at D before turning off the 

 pump. With the pump connexions shewn in fig. 9, the 

 abolition of the. partial vacuum is readily accomplished 

 without danger. 



Fig. 9. Connexions of vacuum pump in author's laboratory. With the tap 

 C in the position shewn a small amount of air is admitted through the 

 narrow tube A. When C is turned through a right angle, full suction 

 through E is obtained. 



(vi.) Disconnect the apparatus and stopper the side neck of A 

 with a cork. 



(vii.) To the thick viscous mass in the flask add 500 cc. of 

 absolute alcohol and heat on a water bath under a reflux 

 condenser until it has dissolved. 



(viii.) Allow the solution to cool somewhat, add 3 to 5 grms. of a 

 good quality animal charcoal, boil on the water bath for 

 10 minutes, and filter hot into a flat-bottomed litre 

 flask. 



