Page:Text-book of Electrochemistry.djvu/179

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��DEGREE OF DISSOCIATION.

��CHAP.

��nitrobenzoic acids and the chloracetic acids. (Phosphoric acid, which may be regarded as a transition electrolyte to the strong acids, also shows great deviations.) We shall return later to a possible explanation of this unexpected phenomenon. Dissociation Equilibrium of Strong Electrolytes. — Up till the present it has unfortunately not been possible to bring the dissociation of strong electrolytes (salts, strong acids, and bases) into perfect agreement with the law of mass action. For this class of substances Eudolphi {10) has changed the Ostwald formula into —

��K =

�� ��(i - >^)vi •

��i,e. he has replaced the factor v in the denominator by \/v. As an example we may give the numbers for silver nitrate. In this case the formula gives values which are in perfect agreement with the experimental results, and the same is true for many other strong electrolytes. The connection expressed in the formula is purely empiric, and no reason can be given for its validity. This anomaly in connection with strong electrolytes ig the most difficult problem of the dissociation theory, and several experienced investigators have endeavoured to solve it, but so far without success.

Silver Nitrate at 25°.

��K

�M».

�fi (obaerred).

�K.

� ��-ST (mean value) = 1'03.

��Another, and still more exact formula connecting the

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