The action of electrolytes on colloidal Prussian blue
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(1) The action of the neutral salts in liberating hydrogen ions from the micelles in prussian blue sols has been investigated by means of (a) electrometric determination of the acidity of the intermicellar liquid and (b) analysis of the coagulum. In particular the influence of the nature and the concentration of the salt has been studied.(2) It is shown that Prussian blue sols exhibit abnormal behaviour, in that the maximum amount of acid liberated varies with the nature of the salt cation. The order of increasing maximum liberation is found to be Li < Na < K < Cs.(3) The results support the hypothesis that, while in the case of lithium the acid is liberated by normal ionic interchange, in the case of the other alkali metals, additional acid is liberated from the interior of the micelles.(4) The influence of the various salts upon the stability of the Sols has been examined and it is shown that the results as a whole are not inconsistent with the view that the amount of hydrogen/(5) The importance of the study of ionic interchange for a general theory of coagulation is discussed.(6) The 'peptisation' of Prussian blue by oxalic acid has been investigated.