1892.] Tonic Velocities. 287 



This method was used to repeat the copper determination, using 

 solutions whose strength was 0*1 gram-equivalent per litre. The 

 specific resistances of the copper and ammonium chlorides were 

 measured by Mtz patriot's method, and came out 157 X 10 9 and 

 117 x 10 9 in C.Gr.S. units respectively. The current was measured by 

 passing it through a previously graduated galvanometer. The 

 velocity of the junction was determined by reading its position at 

 different times by means of a kathetometer. 



When the current was passing upwards, the upward velocity was 



1*70, 1'60, 1*53, 1*43 cm. per hour; mean, 1*57 cm. per hour, 

 and when it was passing downwards, the downward velocity was 

 1*45, 1"65, 1'70 cm. per hour; mean, 1*60 cm. per hour. 



This gives a specific ionic velocity in solutions of O'l gram- equivalent 

 of 



0-000309 cm. f>er sec. 



as compared with Kohlrausch's number for solutions of infinite 

 dilution, 



0-00031 cm. per sec. 



Solutions of potassium bichromate and potassium carbonate have 

 specific resistances which are very nearly indeed (within 3 per cent.) 

 the same for the same strengths, and a solution of carbonate was 

 adjusted in strength till even this small difference between it and a 

 O'l solution of bichromate was much reduced. 



The first point I investigated with these solutions was the influence 

 of change of potential gradient on the velocity. These should, on 

 Kohlrausch's theory, obviously be proportional to each other. 



At first, all the cells available were used. The velocity of the 

 junction when the current passed downwards was 



3-63, 3'39, 3-65, 3'24 cm. per hour ; mean, 3'48 cm. per hour 



in an upward direction. 



When the current was sent upward the velocity was downwards 

 and came out 



3-28, 3'55, 3-45 cm. per hour; mean, 3'43 cm. per hour. 



This gives v l = 0'00048 cm. per sec. 

 An E.M.F. of about one-third that used above was then applied. 



Mean downward velocity, 1'44 cm. per hour. 

 ,, upward 1*29 



Vl 0-00047 cm. per sec. 



