Identification of Organic Compounds. 27 



nating a solvent in vacuo at higher temperatures. The 

 flask a contains a liquid of constant boiling point, which main- 

 tains the interior of the 

 apparatus at constant tem- 

 perature (100 with water, 

 110 with toluene, etc.). 

 The vapour of the boiling 

 solvent circulates round an 

 inner tube b, and is con- 

 tinually condensed in the 

 condenser c, and flows back 

 into a. Into 6 is inserted, 

 by means of a cork fitting 

 into a prolongation of the 

 outer tube, a third tube 

 connected with a retort- 

 shaped vessel, d, by means 

 of a ground-glass joint. 

 This is provided with a 

 side piece and a stop-cock, 

 through which it can be 

 connected with a vacuum 

 pump and manometer, and 

 when the innermost part of the apparatus has been 

 sufficiently evacuated (as determined by the manometer) 

 the stop-cock can be closed. The vessel d contains the 

 absorbing substance, which, when water is to be eliminated 

 from the substance under examination, is usually phos- 

 phorus pentoxide. Other substances, such as sulphuric 

 acid, can be used when organic solvents are to be absorbed. 

 The method of employing this apparatus should be obvious 

 from the above description. 



The substance, in whichever form of apparatus it is 

 dried, is kept during the operation in tubes or small 



Fig. 8. 



