[ 105 ] 
IJI. The Meamvenient of Ionic Velocities in Aqueous t^olutiou^ and (he 
Existence of Complex Ions. 
Tjj B. D. Steele, B.Sc., 1851 Exhibition Scholar {Melboiaiic). 
Communicated bij Professor Lvx\msay, F.R.S. 
lieceived May 10,—Eead Jiuie 6, 1901. 
As early as 1853 Hittoke (‘Pogg. Ann.,’ vol. 89, 181, 1853), discussing tlie results of 
his experiments, emphasised the fact, that a more detailed study of the movements of 
the ions during electrolysis would result in an increased knowledge of the constitu¬ 
tion of salts in solution. 
He himself, in a research extending over a number of years, {ibid., 89, 177, 1853 ; 
98, 1, 185G; lOG, 337 and 513, 1859,) determined the ratio of the velocities of the 
tu o ions for a large number of salts, and the series of measurements has been further 
extended Ijy later investigators. (For tlie original literature on transport number 
determination, see Bein, ‘ Zeitschrift fur Phys. Chemie,’ vol. 27, 1 (1898)). 
The method ado})ted by Hittoef consisted in the direct determination of the 
clianges in concentration which take place during electrolysis in the neighbourhood 
of the electrodes, and depends on a recognition of Faeaday’s law. The increase in 
concentration of the cation at the cathode is pi’oportional to the number of cations 
carried by the current, and similarly for the increase in anion concentration at the 
anode, and these numbers are proportional to the velocities of the cation and the 
anion respectively. 
The ratio of the velocity of the anion to the sum of the velocities of the anion and 
tlie cation p ^ is represented by the symbolyi, which is called the transport number, 
“ U berfuhrungszahl,” of the anion. The corresponding transport number for the 
cation = I — p = - and hence , 
As a result of the examination of simple salts, it has been found that for many 
salts of the most simple type, ey., potassium chloride, the transport number is inde¬ 
pendent of concentration, whereas for a few of this type and for all salts which 
contain a dyad metal as cation, it varies Avith the concentration. The direction of 
VOL. cxovni.—A 3U2. n 13.9.1902. 
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