160 BACTERIAL POISONS. 



filtration by the aid of atmospiieric pressure. The liquid 

 is poured upon a wet cloth supported upon a perforated 

 porcelain funnel, which is connected below with a receiver 

 exhausted by a water-pump or aspirator. In this way 

 rapid filtration is secured, and by repeated washing the 

 extraction is made thorough. The acid alcoholic liquid is 

 now transferred to a special distillation apparatus. 



A large tubulated retort of ten litres capacity is con- 

 nected by means of a cork to a large tubulated receiver. 

 The tubulure of the retort is provided with a small ])er- 

 forated cork, which carries a glass tube finely drawn out 

 and extending to the bottom of the retort. The tubulure 

 of the receiver is connected with Liebig's bulbs containing 

 dilute sulphuric acid (1 to 10), and the bulbs in turn are 

 connected with a water-pump or aspirator. 



In order to prevent the passage of air through the corks, 

 they are covered with animal membrane which has been 

 freed from fat. By means of the aspirator a fine current 

 of air is drawn through the liquid and suffices to keep it 

 constantly agitated. The retort is kept on the water-bath 

 at a temperature of from 28° to 30°. The receiver is kept 

 cold by a current of water In this manner the distilla- 

 tion of the alcohol goes on rapidly and conveniently. More- 

 over, decomposition is so far prevented that volatile bases 

 are never found in the bulbs. 



The aqueous residue, after the removal of the alcohol by 

 distillation, is filtered and extracted with ether as long as 

 anything is dissolved. It is then mixed with powdered 

 glass and evaporated to dryness in vacuo. This residue is 

 repeatedly extracted with absolute alcohol. The alcohol is 

 distilled again in the apparatus already described. The 

 residue is taken up with distilled water and filtered. It is 

 then made alkaline with sodium bicarbonate and repeatedly 

 extracted with ether, benzine, and chloroform. 



In order to obtain the base from the solvent, the greater 

 part may be evaporated on the water-bath and the re- 

 mainder allowed to evaporate spontaneously, or the re- 

 mainder may be treated with dilute hydrochloric acid and 

 the evaporation continued on the water-bath or in vacuo. 



