42 Prof. E. A. Lehfelclt on the 



This means even a greater difference in the discharging- 

 power of the gauze in the two positions than the above 

 numbers indicate, because in the second position the loss of 

 conductivity by recombination while passing up the tube is 

 less than in the first case. 



The difference in the discharging-power of the gauze is 

 explained by the fact that when the carrier has a smaller 

 velocity under an electric force fewer of the carriers come 

 into contact with the gauze by diffusion. It can be shown 

 that for such a gas, when enclosed between parallel planes or 

 in a cylinder, the ratio of conductivity at time t to the initial 

 conductivity varies as e -at '^ where v is the velocity of the 

 carrier under 1 volt per cm. (See Townsend, Phil Mag. 

 May 1898 ) Hence we see that when v is smaller fewer of 

 the carriers are discharged by diffusion as the gas comes up 

 to the gauze and passes through the meshes. 



A In conclusion, I wish to thank Prof. Thomson for his 



Y ' < valuable criticisms and suggestions. 



III. On the Properties of Liquid Mixtures. — Part 1 1 . By E. A . 

 Lehfeldt, Professor of Physics at the E. London Technical 

 College*. 



IN a previous article (Phil. Mag. (5) vol. xl. p. 398) an 

 attempt was made to follow out the consequences of a 

 certain thermodynamic relation between the composition of a 

 liquid mixture, and that of the vapour in equilibrium with it, 

 and the saturation pressure of the system. Experiments 

 were there described on mixtures of benzene with ethyl and 

 methyl acetates in which a small fraction of each mixture was 

 distilled, as nearly as possible at a constant temperature, and 

 the distillate analysed ; these led to an empirical expression 

 connecting the composition of liquid and vapour. Experi- 

 ments were afterwards made to determine the vapour-pressure 

 of similar mixtures by the dynamic method, but they led to 

 unsatisfactory results owing to decomposition of the esters 

 on prolonged boiling. I was able to resume the work in 

 1897, and then chose more stable compounds to work on, 

 viz., benzene and toluene mixed with carbon tetrachloride, as 

 types of normal organic compounds, and benzene and toluene 

 mixed with ethyl alcohol, as type of a so-called " associated " 

 liquid. The experiments to be described here were carried 

 out at the Davy-Faraday laboratory, which the managers of 

 the Eoyal Institution very obligingly placed at my service. 



* Communicated by the Physical Society : read March 11, 1898. 



