Interaction of sodium and calcium salicylates with cationic surfactants

Abstract

Sodium and calcium salicylates have been found to interact with surfactants of the quaternary ammonium type in much the same way as salicylic acid, as stated in a previous report. The interaction produces a marked change in viscosity which increases with salicylate concentration until the system becomes a gel. This increase in viscosity is not related to pH and is reduced with a rise in temperature. This complex interaction is probably due to attraction between the salicylate ion and the cation of the surfactant molecule leading to an increase in size of the surfactant molecule resulting in a rise in viscosity. The change in viscosity is further enhanced by an increase in the electrical charges in the system brought about by the addition of sodium salts, the order of effectiveness of the anion being as follows: citrate > phosphate > sulfate > carbonate > bromide > (except at low concentration) chloride, and by the addition of various sulfates, the order of effectiveness of the cation being as follows: sodium > potassium > ammonium > magnesium > zinc. Phenyl, ethyl, and methyl salicylates fail to show this complex interaction due to the absence of salicylate ion in aqueous solution. In addition, sodium lauryl sulfate and cetomacrogol 1000 do not demonstrate any change in viscosity in the presence of both salicylates. Sodium and calcium salicylates have been found to interact with surfactants of the quaternary ammonium type in much the same way as salicylic acid, as stated in a previous report. The interaction produces a marked change in viscosity which increases with salicylate concentration until the system becomes a gel. This increase in viscosity is not related to pH and is reduced with a rise in temperature. This complex interaction is probably due to attraction between the salicylate ion and the cation of the surfactant molecule leading to an increase in size of the surfactant molecule resulting in a rise in viscosity. The change in viscosity is further enhanced by an increase in the electrical charges in the system brought about by the addition of sodium salts, the order of effectiveness of the anion being as follows: citrate > phosphate > sulfate > carbonate > bromide > (except at low concentration) chloride, and by the addition of various sulfates, the order of effectiveness of the cation being as follows: sodium > potassium > ammonium > magnesium > zinc. Phenyl, ethyl, and methyl salicylates fail to show this complex interaction due to the absence of salicylate ion in aqueous solution. In addition, sodium lauryl sulfate and cetomacrogol 1000 do not demonstrate any change in viscosity in the presence of both salicylates.