難水溶性物質の溶液物性

溶解度, 解離定数及びミセル形成

抄録

Isoextraction and solubility methods were employed to determine the dissociation constant or acidity constant of hardly soluble organic acids. The acidity constants thus obtained were in good agreement with the reported values determined by conventional methods. For dibasic acids, in particular, the successful method was introduced to determine the first dissociation constants where the solubility of undissociated acid was used as a parameter. Both are excellent method to examine the solution properties by taking advantage of constancy of chemical potentials of constituent chemical species of materials. Ionic surfactants also are hardly soluble materials in water at temperatures below the Krafft point. Steep increase in solubility above Krafft point was explained by micellar aggregation where the mass action model was used for micelle formation, and the Krafft point was examined by Gibbs' phase rule. Thenew term of “Micellar Temperature Range (MTR)” was introduced instead of Krafft point for elucidation of extraordinary solubility increase of ionic surfactants.