1978 年 98 巻 6 号 p. 744-751
The activities of Cl- ion (aCl-) of six phenothiazine hydrochlorides (PTZ·HCl) in aqueous solutions were obtained by EMF measurements of Ag-AgCl electrode. Above a concentration specific for each PTZ·HCl, the chemical was considerably adsorbed on to the surface of the electrode with increase in the concentration. The EMF obtained was not equal to the intrinsic EMF corresponding to aCl- in the bulk solution. It was necessary to eliminate the adsorption effect by an appropriate method. The critical micelle concentration (cmc) was determined by means of the crooked points on the plot of log aCl- vs. PTZ·HCl concentration. The crooked point of each PTZ·HCl aqueous solution corresponded to the break point on the plot of pH vs. PTZ·HCl concentration. It was interpreted that the aggregation of PTZH+ ion was accompanied with hydrolysis reaction, PTZH++H2O⇄PTZ+(H3O)+. Taking the hydrolysis into account, the abnormality of aCl- in the region just above cmc was thermodynamically explained.