Reversible Emulsions. 



3 



mine more accurately the relative capacity possessed by different 

 positive ions to inhibit the solvent effect of negative ions on the 

 stabilizing fatty acid film formed by contact between aqueous 

 and oil phases, solutions containing varying proportions of positive 

 and negative ions were run through oil from a Traube stalag- 

 mometer. By observing the relative number of drops formed by 

 equal volumes of different solutions, or the concentration of solu- 

 tions giving an equal number of drops, it was possible to determine 

 the relative facility with which films of this nature were formed 

 and maintained. It was found that equal volumes of ra/iooo 

 NaOH, ra/50 Ca(OH) 2 and m/10 Fe(OH) 3 gave an equal number 

 of drops. Furthermore the concentrations of NaCl, CaCU and 

 FeCl3 required to precipitate a sodium oleate solution were found 

 to be .4 M, .02 M, and .004 M, respectively. Since these ratios 

 of 100 : 5 : 1 are the inverse of those observed above, and since 

 they represent approximately the logarithmic ratio observed by 

 Hardy for the precipitation of negatively charged colloids by 

 mono-, di-, and trivalent kations, it may be concluded that the 

 maintenance of equilibrium of an aqueous oil system of this type 

 depends upon the relative proportion of kations and anions present 

 in the system and adsorbed by the stabilizing film and the extent 

 to which the adsorbed kations, by counteracting the solvent 

 action of adsorbed anions promote the continuity of the stabilizing 

 film. From the experiments of Loeb, and his pupils, it must be 

 concluded that di- and trivalent kations exert a far greater effect 

 than monovalent kations in maintaining the equilibrium of bio- 

 logical systems. Since these ratios are frequently approximately 

 logarithmic, the question suggests itself whether the positive ions 

 concerned do not function by counteracting the destructive effect 

 of negative ions on protoplasmic films or membranes in a manner 

 similar to that indicated above for purely physical systems. 



