of Miscible Liquids by Distillation. 



641 



3. In the experimental investigation of the thermal effi- 

 ciency which can be obtained in the laboratory, a mixture of 

 40 c.c. of " crystallized " benzene with 10 c.c. of reputed pure 

 toluene was boiled in a 100-c.c. vacuum flask as still. For 



Fig-. 2. 



The Heat required to distil Benzene from mixtures of Benzene 

 and Toluene. 



50 

 MASS PER CENT 



BENZENE 

 TOLUENE 



the first experiments a Dufton column* was constructed in a 

 glass tube, 105 cm. in length and 0'46-cm. bore. Heat was 

 supplied electrically by means of a platinoid spiral immersed in 

 the liquid and the rate of heating was determined by measure- 

 ment of the current and the potential difference, calibration 

 being effected by heating a known mass of water in the 

 flask. The benzene condensed was collected in a burette 

 and observations of its volume were made at five-minute 

 intervals. A thermometer placed in the top of the column 

 showed the temperature of the vapour and indicated the 

 * S. F. Dufton. loc. cit. 



