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Soil removal data were developed for five laboratory methods and one practical wash test method, utilizing a single standardized soil test fabrie. The degree of correlation between the methods is good considering the variety of machines and procedures used. Better correlation between methods was obtained in hard than in soft water, attributable to the higher solution concentration used in the hard water tests. The rating given the four detergents by the test methods was fairly uniform; the hard water data again were more concordant. Under the conditions used which were optimum for soap, the order of effectiveness was: soap, built nonionic and built alkyl aryl sulfonate, and loralkyl sodium sulfate. Ordinarily, solution concentration-water hardness curves would be developed for complete evaluation, but the scope of this work precluded this procedure. The test variation for the five laboratory methods was of the same degree. The practical concentional washer test gave coefficients of variation roughly triple those for the laboratory methods. This difference is largely attributable to poorer test control of conditions such as degree and kind of soil of the test load. Even though different test washing machines were used, it appears that adjustment of factors such as wash time and ratio of fabric to solution might provide closer correlation between methods.

A dynamic foam test for evaluation of hand-dish-washing compositions has been developed which gives good correlation with semipractical plate washing tests. Properties measured in the dynamic tests are foam build-up index, foaming capacity, and stability of foam to soil.

It was demonstrated that the average soil removal values for the four 10-minute wash Launderometer method could probably be essentially duplicated by a single 3-minute Terg-O-Tometer wash and one 2-minute rinse. The 3-minute Terg-O-Tometer method did not result in the same comparative rating of four detergents, but a series of tests with several other detergents using a 5-minute wash and a 5-minute rinse (using for comparison purposes a standard detergent) resulted in quite effective ratings. Of 13 detergents tested over a period of time, the two test methods provided soil removal values identical within a 95% confidence limit. These data indicate that a satisfactory technique can be developed using the Terg-O-Tometer, which would provide soil removal values and ratings of detergents closely paralleling the results obtained by the Launderometer multiple-wash method.

The ability of dilute surfactant solutions to solubilize water-insoluble substances to form stable systems is termed solubilization. Reviewed are the mechanism, methods for measurement, and temperature effect. Discussed in detail are surfactant structure and solubilizates, and the principles of solubilization involved. The application of solubilization to detergency operations is discussed broadly. It is concluded that solubilization is a minor, difficultly measurable factor in the large majority of aqueous cleaning operations.

Substrates investigated were glass, quartz, porcelain, steel, stainless steel, aluminum, polyethylene, methylmethacrylate, Nylon, and Teflon. Radiotagged (C-14) soils used were algal protein, stearic acid, and tristearin. Soil removal curves showed that Nylon, Teflon, methacrylate, and stainless steel had few soil-adsorption sites and that the adsorption was of an ion-exchange type. Algal protein and stearic acid soils appeared to adsorb through an ion-exchange type mechanism, with most substrates, while tristearin showed a van der Waals' type of adsorption with glass, quartz, steel, and aluminum. Conclusions as to adsorption type were based upon the shape of the soil-removal curves. Adsorption studies showed that both anionic and nonionic surfactants were adsorbed by glass, procelain, steel, and aluminum surfaces, apparently by an ion-exchange type of adsorption. The character of the surfactant adsorbed affected the degree of removal of subsequently applied soil; the more hydrophilie surfactants permitted easier soil-removal. Tripolyphosphate, orthophosphate, and ethylenediamine tetraacetate anions and tetraethylammonium cations were adsorbed by these same substrates and influenced the ease of removal of subsequently applied soil. Pretreatment of substrate by alkali generally increased the ion or surfactant adsorption more than acid-pretreated surfaces, and rather marked similarities between the adsorption sites of glass and quartz were apparent from acid pretreatment. Stearic acid soiled substrates were cleaned by a preferential displacement mechanism; the soil was rolled up into globules. Tristearin-soiled surfaces were cleaned by a similar mechanism.

Using two model soil-detergent systems (hard substrate/triglyceride; cotton/fat, mineral oil, graphite) it was shown that soil removal begins at, or near, critical micelle concentration (eme), confirming the work of other investigators with different systems. Maximum detergency occurs at concentrations considerably in excess of cmc, varying some 6 to 10 times cmc for different surfactants. An equation for soil removal showed excellent fit of experimental values for both detergency systems. Direct correlation between cmc, solubilization (of several materials), and soil removal was demonstrated. Marked differences between surfactant type and solubilization of triglycerides were found. The nonionic surfactants were excellent solubilizers for triolein correlating with their effective soil removal. Neither sodium oleate nor sodium tripolyphosphate effectively solubilized the triglyceride but both are effective soil removers, suggesting that their soil removal mechanism differs from the nonionics, possibly as an emulsification or displacement mechanism. Solubilization of triglyceride occurs most effectively considerably in excess of cmc.

The measurement of critical micelle concentration is discussed from the viewpoint of practical detergent application. Micelles are briefly characterized, and methods for measurement are discussed. The difficulties of measuring nonionic surfactant critical concentrations is indicated, and several applicable methods are described. The practical detergent applications of critical micelle concentration (cmc), as affected by electrolyte builder combinations, are illustrated. A concise summary of the principles governing micelle formation has been developed.

Preliminary investigation of several test procedures resulted in the selection of the Liss-Hilton reflectance method. A white vinyl tile substrate was selected and the test method optimized at cleaning efficiencies of approximately 30% for water and 80% for selected detergent compositions. Within-series and between-series variations, in general, met a required 2% maximum. Between-laboratories data were slightly more variable. Utilizing the corresponding confidence limit factor, as few as three test panels per detergent may be used to compare detergent cleaning efficiencies.

Previous papers have reported radiotagged fatty soil removal from glass either by solvents or by aqueous solutions of sodium tripolyphosphate and other builders. This paper provies soil-removal data for aqueous systems of both pure and built surfactant compositions of the nonionic and alkylbenzene sulfonate types. In general, nonionics are the most effective detergents for the system fatty soil/glass; the 10-mole ethylene oxide adduct products show peak soil-removal. Nonionic surfactants appear most effective for soil removal when used in baths closely approaching their cloud-points. Though modification of hydrophobe by EO addition can affect cloud point, peak soil-removal effectiveness seems to be controlled by hydrophobe selection. Highest soil removal for the alkylbenzene series occurred with the longer alkyl chain (pentadecyl). Admixture of surfactant and sodium tripolyphosphate provided synergistic compositions with certain 10-EO surfactants. Building of anionics markedly improved soil removal over the pure material but seldom exceeded the removal by STP alone.

It is shown that the reported differences in anionic surfactant adsorption on cotton can be largely attributed to the presence of variable amounts of natural wax on the fiber surface. High adsorption values with peaks near critical micelle concentration (cmc) result from surfactant adsorption on the wax surface. Wax-free surfaces fail either to show the same high maxima or the same relative magnitude of adsorption. At surfactant cmc the adsorption relationship for waxy cotton (millimoles/g. of cotton) cationic: nonionic: anionic was roughly 66 to 17 to 74. For dewaxed cotton, this became 40 to 10 to nil. Confirming the findings of others, no adsorption by cotton of sodium tripolyphosphate occurs either with waxy or wax-free cotton. Also addition of tripolyphosphate decreased the adsorption of several anionic surfactants. At concentrations greater than cmc and at sufficiently-high solution temperature, anionic surfactants can solubilize cotton wax, leaving a less waxy substrate upon which adsorption is then reduced.

Both algal protein and stearic acid soils are removed by water alone to near a 50% level; retained soil then becomes more difficult to remove. The bonding of protein soil to glass is stronger than that of tristearin, with indications that stearic acid soil is als slightly more adherent. The shape of the protein soil removal curves lacks the sigmoid shape of the tristearin or stearic acid soils, suggesting either the absence of sharp dependence upon critical micelle concentration, or the existence of adsorption largely at an essentially single energetic level. Both these soils are generally more effectively removed by anionic surfactants than was tristearin. Sodium tripolyphosphate is quite effective for removal of both soils, but combination with surfactants failed to provide the synergistic combinations found in tristearin removal. Nevertheless surfactant soil removal was improved by STP combination.

The acid clay catalyzed dimerization of tall oil fatty acids and oleic acid yields commercial products which are complex mixtures of monomers, dimers, trimers, and higher polymers of various structures. Analyses for monomer, dimer, and trimer concentrations are important to ensure good quality control and reproducible end use performance. Techniques for direct determination of monomer, dimer, and trimer acids by gel permeation chromatography are presented. The components are separated using Bio Beads SX-2 gel. Heptanoic acid is used as an internal standard. The standard deviations for determination of dimer, trimer, and monomer are 1.0, 0.4, and 0.2% respectively. Calibration was accomplished using dimer and trimer fractions isolated from a preparative scale chromatographic system. It is suggested that a measure of higher polymeric acids can be obtained by difference after correction for neutral materials.

The mechanism of radio-tagged tristearin removal from a glass substrate by sodium tripolyphosphate is primarily one of preferential displacement. Tristearin removal by STP appears to be a competition for primary polar adsorption sites: being the more polar, STP displaces the soil. Continuous soil films are more slowly removed than spotty soil films because initially fewer accessible adsorption sites are available for displacement attack by STP. It is believed that emulsification of these heavy films occurs initially by the ‘stripping” or preferential displacement by STP of the adsorbed monolayer at a site, followed by a rolling up of coherent soil along with the desorbed monolayer, resulting in a degree of emulsification. In addition to its sequestrant water-softening action, previously considered its main function, and its detersive effectiveness, another very important feature has been discovered. Tripolyphosphate (and sequestrant type of anion) adsorbs on a glass surface and reduces the tenacity of subsequent fatty resoiling. This may account to a considerable degree for the demonstratedly high practical cleansing effectiveness of the compound. Adsorption of STP is not by a base exchange mechanism for quartz also displays the same effect as glass. It seems apprarent that the same type of adsorption sites exists on both glass and quartz surfaces though those on quartz suggest either a stronger adsorption of a higher energy level or a larger number of adsorption sites. These data demonstrate the relatively high detersive efficiency of the polyphosphates for this soil/substrate system. Sodium metasilicate and sodium carbonate fall considerably lower in soil-removal value.