Surface tension measurements in solvent sulphuric acid

Abstract

Measurements by the pendant drop technique confirm that the self-dissociation of sulphuric acid is relatively unimportant in determining the shape of the surface tension (γ)vs. composition curve in the neighbourhood of the pure solvent composition. The surface tension (γ for 100% sulphuric acid at 30°= 50·6 dyne. cm.^–1) is hardly affected by sulphur trioxide, but water causes a marked increase. Micellization is indicated in hexadecylamine solutions (critical micelle concentration 0·017m at 30°), which thus confirms the cryoscopic observations of Leisten and Walton. Dodecylamine, on the other hand, forms no micelles up to 0·2m in the pure solvent, as shown by the drop-weight method and by cryoscopy; but micelles are probably formed with this solute in more aqueous (98%) acids.