Solubilization of fatty soils by a radiotracer technique

A technique for measurement of solubilized radiotagged triolein and tristearin fatty soils is described. By using surfactant solutions under standardized conditions of temperature and agitation, the solubilized soils are removed from emulsified materials by filtration through 0.1 and 0.01 micron-pore size of filters. The radiotagged fat is recovered by solvent extraction from the clear filtrate by salting-out under centrifugal force and is measured by conventional counting technique. The nonionic alkanol- and alkylphenol-ethylene oxide (EO) adducts solubilized up to 0.058% triolein (weight percentage at 75°C.) while anionic surfactant and sodium tripolyphosphate solubilization was negligible. These findings suggest for these nonionics that solubilization is one of the main, if not the controlling factor in the mechanism of soil removal. Nonionic solubilization was at a maximum for 10 molar EO adducts and at near cloud-point temperatures. For the same surfactant more triolein than tristearin was solubilized, possibly on account of spatial considerations. For tridecanol-10 EO at 0.25% the heat of solubilization of triolein, ΔH_s, was 15 kcal/mole while the heat of micellization of the adduct was 1.3 kcal/mole of adduct. Differences in the colloidal ion lengths of the micelles and their aggregation numbers may explain the differences in solubilization between the anionic and nonionic surfactants tested.