Page:Text-book of Electrochemistry.djvu/96

 VI.

��DISTRIBUTION LAW.

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��deviations occur, which, however, do not attain a particu- larly high value. The influence of temperature on this

distribution ratio is such that — increases with rising tem-

��perature.

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��Other experiments were made on the distribution of bromine and iodine between carbon disulphide and water, and of benzoic acid, oxalic acid, malic acid, and tartaric acid between ether and water.

If an excess of solid succinic acid be shaken with water and ether, two saturated solutions are formed ; and if the excess of solid be now removed, the equilibrium must nevei-- theless persist. The distribution coefficient of succinic acid between water and ether must, therefore, be the ratio of the solubilities of this substance in the two solvents. It must, however, be remembered that in this case the water is not free from dissolved ether, and the ether is not free from dis- solved water, and consequently perfect agreement cannot be expected between the distribution result and that obtained when the solubilities in the pure solvents are used.

If a substance (or, more strictly, one kind of molecule) is present in two phases (e.g. in aqueous and ethereal solution), the concentration in one phase must stand to the concentra- tion in the other phase in a constant ratio, provided that the temperature is kept constant (5). This general statement embraces Henry's law as a special case in which one of the phases is gaseous.

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