ANALYTICAL PROBLEMS IN THE PRODUCTION OF ALPHA-SULFONATED FATTY-ACID METHYL-ESTERS

Heterophase titration with Hyamine 1622 in the presence of methylene blue and bromocresol green was rued to determine the content of mono- and disodium salts in the products of sulphonation of hydrogenated fatty acids of low erucic rape-seed oil. Model investigations on standard substances and their mixtures enabled the authors to establish that only the monosodium salt of alpha-sulphonated fatty acid methyl ester is titrated, in the presence of bromocresol green, the disodium salt of the alpha-sulphonated compound not being determined. According to the authors this is due to the physicochemical properties, e.g. dissociation constants, of bromocresol green and the disodium salt, and not to the difference in the molecular weights of the indicator and the surfactant being determined as has been suggested by some researchers.