Thermodynamical Theory of Solutions. 933 



2. These slow moving particles can be accelerated at will, 

 the minimum potential difference required to give them a 

 sufficient velocity to affect the plate being about 500 volts 

 per centimetre. 



3. There is secondary radiation present as well as 

 primary — both straight lines and their continuations as 

 parabolas are shown on a few of the photographs. 



4. The value of e/m is the same for the various carriers as 

 that found by Sir J. J. Thomson in the case of the positive 

 rays formed by the ordinary perforated cathode w T ith high 

 potential discharge. 



5. The greater the acceleration the more clearly cut and 

 well defined are the photographs, also the nearer the para- 

 bolas extend to the origin. 



6. This investigation does not show a negative counter- 

 part to any of the curves. 



7. The work thus far has been with residual air only. 



In conclusion I wish to express my appreciation to 

 Professor Sir J. J. Thomson for the problem and the main 

 line of attack, also for the facilities of the Cavendish 

 Laboratory that he so kindly placed at my disposal. 



August 17, 1911. 



XC. On the Application of the Theory of Chemical Potential 

 to the Thermodynamical Theory of Solutions. By S. A. 

 Shorter, B.Sc, Assistant Lecturer in Physics in the 

 University of Leeds. — Part I. The General Theory of 

 Chemical Potential in a Binary System. Osmotic Pressure 

 and Vapour-Pressure of Solutions*. 



GIBBS'S Theory of Chemical Potential t is a very power- 

 ful instrument for the solution of many thermodynamical 

 problems. This instrument, however, seems never to have 

 been applied to the solution of many important problems in 

 the Theory of Solutions. Thus many attempts have been 

 made to deduce an expression connecting the osmotic 

 pressure and vapour-pressure of a concentrated solution. 

 Nearly all the expressions which have been deduced are 

 approximate ; one well-known expression is quite wrong. In 

 only one case + has an exact expression been deduced con- 

 necting the osmotic pressure and vapour-pressure of a 



* Communicated by the Author. 



t " On the Equilibrium of Heterogeneous Substances," Collected 

 Works, vol. i. p. 55. 



% Porter, Roy. Soc. Proc. A. vol. lxxix. p. 519 (1907). 



Phil. May. S. 6. Vol. 22. No. 132. Dec. 1911. 3 Q 



