Page:Text-book of Electrochemistry.djvu/74

 V.

��DISSOCIATION OF ELECTROLYTES.

��Beckmann {10) show.* Thus, for instance, if the concentra- tion of ethyl alcohol be increased from 0*2 per cent, to 6 \m cent., its molecular weight in benzene increases from 46 to 128, and in acetic acid from 47 to 54, whilst in water it i^maius almost constant.

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�Acetic add

�Phenol

�Ethyl alcohol

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�weight. 144 '

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� ��Dissociation of Electroljrtes.— The deviations which have been found for electrolytes in aqueous solution must be explained otherwise than by the assumption that complex formation takes place. Van't Hoflf limited himself to showing that most salts, as well as the strong acids and bases, or, generally, strong electrolytes, give too large a molecular lowering of the freezing point, without discussing the cause. Since that time different explanations have been brought forward. It has been assumed that the molecules of the solvent camcombine with those of the dissolved substance, or exert an attraction on them, but none of these hypotheses has been able to withstand full investigation, except that one

' In the gaseous condition, too, the fatty acids tend to form double molecules (s^e p. 42). In a less degree this applies also to alcohols. Also for the gaseous state theory predicts, and in this is confirmed by experiment, that fewer molecules combine to complexes the lower the concentration is. In a highly concentrated (or liquid) form the substances mentioned aggregate to a great extent to molecular complexes, as the results obtained in connection with the capillary forces and at the critical point prove.

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