In the following table, the relative activities of acids, in accelerating the decomposition of methyl acetate by water, are contrasted, in a similar fashion, with their relative conductivities. The conductivities of acids depend to such an extent on the concentration of hydrogen-ion, which moves five times, or more, faster than the anions and carries therefore the greater part of the current, that the conductivities of acids, in equivalent concentrations, may be considered an approximate measure of their relative degrees of ionization and ‹of the concentrations of hydrogen-ion›. For the purpose of comparison the activity and the conductivity of molar hydrochloric acid are both represented by 100. All the acids were used in normal solutions.
CHEMICAL ACTIVITY OF ACIDS AND THEIR IONIZATION.[A]
Acid. Activity. Conductivity. Hydrochloric acid 100 100 Nitric acid 92 100 Sulphuric acid 74 65 Acetic acid 0.3 0.4 Formic acid 1.3 1.7 Chloracetic acid 4.3 4.9 Tartaric acid 2.3 2.3
A. Whetham, ‹Theory of Solutions›, p. 338.
In the following chapters and, indeed, throughout our further work, we shall continually meet additional instances of the quantitative relation between chemical activity and ionization. In fact, the results obtained in the field of quantitative measurement of chemical action, of which the above are single instances, have demonstrated, more than anything else, the value of the theory of ionization to chemistry and the necessity of taking it into account in expressing the results of chemical action in mathematical terms. [p083]
«Summary.»—Measurements made, then, in three great and independent fields of investigation, ‹electrical conductivity›, ‹osmotic pressure› and the allied relations, and ‹chemical activity›, bring independent testimony to the correctness of the fundamental assumptions of Arrhenius's theory of ionization. In the quantitative study of solutions of electrolytes, wherever secondary disturbing influences are eliminated or are taken into account as far as possible, the three lines of investigation give results which agree satisfactorily[143] as to the degree of ionization of the electrolytes under examination. With the aid of this theory, ‹predictions› of the course of chemical action may now be made more definitely and with more assurance than ever before in the history of chemistry.
