TOLMAN. — ELECTROMOTIVE FORCE PRODUCED IN SOLUTIONS. 117 



equal to hgd, we must add to the electromotive force Ei as given in ecjua- 

 tion (3), the electromotive force E2 given by the equation below, which is 

 derived by ecjuating the external electrical work to the work produced 

 by the change in volume 



10^ EiF = 3Ij {vj - VjJ hgd. 

 Noticing that 



= T 



u + V 

 we obtain 



10^ {E\ + E,) F= kg [ TMc (1 - %d) + TMi (1 - Vid) -3Ij (1 - v,^d)] 

 or 10^ EF= hgirjis (1 - r,c?) - i)7, (1 - Vj/l)] , 



which is the same equation we originally obtained by thermodynamic 

 reasoning. 



The real interest attached to this kinetic consideration is the almost 

 absolute proof it offers that some degree of dissociation or at least 

 polarization of the salt molecules exists in aqueous solutions. Since 

 unless the positive and negative components of the salt can move rela- 

 tive to one another we cannot see how a potential gradient is set up 

 by centrifugal separation. The method gives, of course, no idea of the 

 magnitude of the degree of ionization. 



4. Description of Apparatus. 



The general arrangement of the rotating apparatus is shown in Fig- 

 ure 1. It consists of a steam turbine A, with vertical shaft, driving the 

 rotator B, which contains the tubes of solution. Electrical connection 

 with the electrodes in the solution was made through the mercury 

 contacts C. 



The Steam Turbine. 



The turbine used was a thirty horse-power de Laval loaned for this 

 investigation by the General Electric Co. The turbine wheel was ten 

 inches in diameter. A 2-inch steam pipe D leads into the annular 

 space E from which the nozzles lead up to the turbine wheel. The 

 holes F are opposite the openings to the nozzles and are threaded to 

 receive the bonnets of the nozzle valves (not shown in the drawing). 

 A 3-inch exhaust pipe leads from the exhaust chamber G, on the side 

 away from that shown in the drawing. The turbine is supported on 

 the legs H, bolted to the cross beams I. It is also bolted to the block 

 J. Largely for the sake of safety, the apparatus was re-designed 



