IN AQUEOUS SOLUTION, AND THE EXISTENCE OE COMPLEX IONS. 
Ill 
Ill this eijiiatioii, 
C = the current as measured by the galvaiioiiieter. 
A = the sectional area of the conducting medium. 
n = the normality of the solution. 
rj = the electro-chemical equivalent of liydrogen. 
U and V = the observed velocity of the cation and anion respectively. 
u and V — the specific velocities of the cation and anion. 
X = the coeliicient of ionization. 
TT = the fall in potential or potential slope. 
In Massox’s paper it is shown that the ratio -^—777 = 1 for a number of salts 
of the most simple ty] 3 e ; hut here again salts of the type of magnesium sulphate 
give values for this ratio (when measured in gelatine) differing considerably from 
unity, and similarly for more concentrated solutions of potassium, sodium, and 
lithium sulphates. 
Both Masson and Whetham employ as indicators solutions which contain ions 
having a characteristic colour. The employment of these necessarily limits the 
method, since there do not exist many coloured anions from which to select, and 
none which do not give a precijDitate with the heavy metals and the metals of the 
alkaline earth group. Whetham’s first method is subject to the further limitation 
that there are not many pairs of solutions that fulfil all the conditions necessary for 
its application ; it also does not allow for the changes in concentration that will take 
place, unless the transport numbers as well as the conductivities of the two salts are 
identical. 
Nernst (‘Zeitschrift fur Electro-chemie,’ 3, 308, 1807) has described a lecture 
experiment, 'vTiicli shows the motion of a coloured margin, that Ijetween potassium 
2 )ermanganate and potassium nitrate. The success of the experiment depends on 
the selection of pairs of solutions whose ions on eitlier side of the Ijoundary possess 
the same specific velocities, a condition that is fulfilled in the case of the ions 
MnO^ and NO 3 . 
The author (Steele, ‘ Chem. Soc. Journ.,’ 79, 414, 1901) has succeeded in extending 
Masson’s method in two directions. 
The first extension consists in the substitution of aqueous for gelatine solutions 
of the salt to Ije measured. By this means many salts winch will not form solid 
jellies with gelatine may he investigated. The second depends on the fact that it 
has been found possible to observe the boundary between two colourless solutions, 
on account of their difierence in refracti\'e index, tlius rendeiing the use of tlie 
coloured indicator solutions unnecessary. 
The method compares the velocity of the anion and cation, and therefore determines 
