Page:Outlines of Physical Chemistry - 1899.djvu/270

 ��OUTLINES OF PHYSICAL CHEMISTKY

��III. HYDROLYTIC DISSOCIATION

In the preceding chapters we have shown that each acid, and probably each base, possesses an activity peculiar to itself, and it manifests this with a constant intensity in a series of reactions. The prime cause of this behaviour is revealed to us by a study of the electric conductivities. The following table contains the conductivities of some acids in normal aqueous solution, 1 hydrochloric acid being taken as the standard of comparison :

��Hydrochloric

�Acetic

�Hydrobromic

�Monochloracetic

�Nitric

�Dichloracetic.

�Sulphuric

�Trichloracetic.

�Ethylsulphonic

�Oxalic

�Benzenesulphonic

�Tartaric.

�Formic

� � ��With the exception of some digressions due to the con- ditions of the experiment, 2 this series of members is abso- lutely similar to that given on page 250. The activity of the acids is, therefore, proportional to their conductivity, that is to say, to their degree of dissociation. Hence it seems

��1 One equivalent per litre.

2 Particularly to the different concentration of the solutions which are used for the experiments on saponification, inversion, neutralisation, and electric conductivity.

3 We therefore measure the relative strengths of dissolved acids by their molecular conductivity, or rather by their degree of dissocia- tion. It must, however, be admitted that this method of measuring the strength of acids is not of a very general character, inasmuch as it depends too greatly on the conditions of the experiment, and particularly on the dilution of the solutions examined. If we com- pare, for instance, hydrochloric and acetic acids, we find that in

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