Abstract
The behavior of aromatic sulfonic acids in the aqueous solution was studied in relation to the molecular structure.
The mobilities of the aromatic sulfonate ions were measured by the Tiselius electrophoretic apparatus.
The mobilities of the disulfonate ions were found to be much larger than that of the monosulfonate ions. This may be due to the larger charge quantity as well as the larger disturbance of arrangement of surrounding water of aromatic rings of disulonic acid than those in the monosulfonate. But the rate of increment of mobilities with the increase of concentration of disulfonate ions were equal or less than that of monosulfonate ions in spite of the larger reduction of ionic atmosphere. This difference may be ascribed to the repulsion of sulfonate ions themselves. The larger the concentration of the sulfonate ion in the aqueous solution of sodium chloride of definite amount, the larger the mobility of the respective ion. A factor explaining this phenomenon may be the increase in effective charge induced by the decrease of ratios of sulfonate and sodium chloride. When the groups such as NH2 or OH are introduced into aromatic ring, the ratio of increment of the mobility increased. For this observation a rationale is advanced in which the disturbance of arrangement of surrounding water of aromatic ring by these groups causes the increase of mobility. The mobility of benzidine systems as well as aniline systems coupled with the same aromatic sulfonic acid in addition to the aromatic sulfonic acid itself were compared and the results are obtained in which the ratio of increment of mobilities increase in the order of; aromatic sulfonic acid, aniline systems, benzidine systems.
