Page:Outlines of Physical Chemistry - 1899.djvu/273

 HYBROLYTIC EQUILIBRIUM

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��The equation of equilibrium for binary electrolytes, just confirmed for acetic acid, is generally applicable to mono- basic acids of moderate conductivity (Ostwald, 1889). The equation also holds good for dibasic acids provided the dissociation does not reach 50 per cent. This fact shows that dibasic acids at the commencement of their dissociation behave like binary electrolytes and decompose according to the equation

HAH + H 2 =HOH + HAH

Succinic acid and even sulphuric acid belong to this category. In the solutions employed by Thomsen the sul- phuric acid was not dissociated to a greater extent than

50 to 60 per cent., and this explains its comparatively low

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avidity : it would react as HS0 4 H so, that a half gram- molecule, from the point of view of avidity, would only be equal to a half -equivalent.

For binary electrolytes of high conductivity, neutral salts, inorganic acids and bases, the application of the equation of equilibrium leads to irregularities. For tertiary

��* We see that the dilution and the degree of dissociation increase

simultaneously. The reason of this is, that by the addition of water

the active mass of the dissociating agent is increased. — We see

besides that an increase in the volume of the solution diminishes the value of the ratio — - in such a way that the equilibrium can

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only be re-established by an increase in the dissociation.

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