ON ELECTROLYSIS AND ELECTRO-CHEMISTRY. 217 
sive power and conductivity is said to be almost conclusive evidence against 
the theory. Armstrong suggests instead a theory of electrolysis based 
upon the formation and decomposition of molecular aggregates under the 
influence of residual affinity, and he has in his favour, so far as it goes, 
the evidence given on p. 204 for the existence of definite hydrates in 
solution. But, av he himself says, his objections to the dissociation theory 
cannot be regarded as definite experimental reasons which make the 
theory untenable, but rather as suggesting knotty points which those in 
favour of the theory have to deal with. Arrhenius has replied to the 
objections,' and has to a certain extent met that based on the constants of 
diffusion ; the others can only be definitely decided upon by the sub- 
sequent development of the theory. 
Some considerable advance has already been made. Ostwald 
(‘Zeitschr. f. phys. Chem.’ vol. 2, p. 270) explains that the theory ac- 
counts satisfactorily for the following six relations, which were previously 
‘accepted as empirical generalisations of the results of observation :— 
1. The molecular conductivity of all electrolytes increases with in- 
creasing dilution, and approaches asymptotically a maximum value. 
2. These maximum values on the one hand for acids, secondly for 
bases, and thirdly for salts (referred to equivalent quantities) are of the 
same order of magnitude, but not strictly equal. 
3. The maximum values can be represented as the sum of two magni- 
tudes, of which the one depends only on the positive, the other only on the 
negative ion (Kohlrausch’s law). 
4, For electrolytes of higher concentrations as well as for weak acids 
and bases the previous statement does not hold ; an approximation thereto 
is apparent when one compares groups of salts whose ions are of equal 
valency. 
5. Electrolytes of low conductivity, such as weak acids and bases, 
have their molecular conductivity very rapidly increased with increasing 
dilution. With monobasic acids and normal bases the conductivity 
increases in proportion to the square root of the volume of solvent. 
6. The increase of molecular conductivity takes place with all mono- 
basic acids and monovalent bases, according to the same law. If one com- 
pares such electrolytes, for dilutions at which these conductivities are 
equal fractions of the maximum, the degrees of dilution (or volumes 
corresponding to one gramme-molecule) are in constant ratio. 
In order to prove these statements from the dissociation theory, 
Ostwald pushes the analogy between the state of the molecules in a solu- 
tion and the state of gaseous molecules a step further. Adopting, from 
the theory of dissociation of gases (Ostwald’s ‘ Lehrbuch,’ 2, p. 723), 
the formula R log ? = pt const., where p is the pressure of the undisso- 
Pipe 
ciated part, p, and p, the partial pressures of the dissociated constituents, 
and assuming the temperature to be constant and the two sets of ions to be 
equally numerous, he obtains an equation p/p,?=c, which, on the assump- 
tion of identity or strict analogy of molecular constitution in solutions, ap- 
plies to the dissociation of a salt in a solvent. Transforming this equation 
in terms of molecular conductivities, on the assumption that these depend 
' Electrician, Sept. 7, 1888. 
* The theory is also criticised by E. Wiedemann, Zitschr. fiir ph. Chem. vol. 2, 
p. 241, 1888. . 
