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The activity of three quaternary ammonium salts, dodecyltrimethylammonium chloride, dodecyldimethylethylammonium chloride and dodecylpyridinium chloride, against M. aureus, E. coliand C. albicanshas been determined and correlated with the surface properties of these compounds. The Ferguson principle has been applied by using surface concentration to estimate thermodynamic activity. Results obtained for the three quaternary ammonium salts and a particular micro-organism species were found to be in good agreement with each other when microbiological and surface studies were conducted under identical conditions.

Surface pressure-area isotherms of monolayers of the half-esters of poly (methyl vinyl ether/maleic anhydride)(PVM/ MA) on aqueous subphases indicate interactions between the polymer and various water-soluble diester plasticizers. Polymer monolayers, either alone or in the presence of plasticizer, have no effect on water evaporation. Certain monolayer properties of the PVM/MA derivatives are related to properties of the polymers in free films.

The adsorption of 3 quaternary ammonium salts, dodecylpyridinium chloride, dodecyltrimethylammonium chloride, and dodecyldimethylethylammonium chloride, has been measured at the hexane-, octane-, decane-, dodecane-, and tetradecane-0.1M KC1 interface. Adsorption appears to be influenced by interaction between the oil and both the nonpolar and polar portions of the surface-active agents, even though the surface-active agents are not soluble in the oils. The relative effect of chain length of the oil on surface concentration is a function of the bulk concentration of the quaternary ammonium salts.

The interactions between the dye, sodium p-(2-hydroxy-1-naphthylazo)benzenesulfonate (orange II) and four long chain quaternary ammonium salts—1-hexadecylpyri-dinium chloride, dodecylquinolinium bromide, (2-phenoxyethyl)dodecyldimethyl-ammonium bromide, and (diisobutylphenoxyethoxyethyl)dimethylbenzylammonium chloride—have been investiagated. The stoichiometry of these interactions has been deermined to be 1:1 at pH values ranging from 0.73 to 12.91, except for the reaction involving the hexadecylpyridinium ion above pH 12.34, where the stoichiometry of dye to quaternary ammonium ion is 1:2. The solubility of the various solid compounds has been determined at 25, 30, 35, and 40°. From these data, the thermodynamic functions, ΔH°, ΔS°, and ΔF° have been calculated. Marked solubilization of these compounds has been observed in the presence of excess common quaternary ammonium ion at or near the critical micelle concentration of the particular long chain ion. The significance of these results is discussed.

The surface tension of solutions containing selected long-chain quaternary ammonium compounds, having the same chain-length and counterion but differing in their polar group, was measured using the drop-volume method. The Gibbs adsorption equation was applied to obtain the surface concentration for each bulk concentration used. Data obtained in very dilute solutions conform to the equation of state for an ideal two-dimensional “gaseous” monomolecular film; whereas at higher concentrations, the films are in a “liquid-condensed” state. The standard free energy, entropy, and enthalpy for adsorption were calculated from data obtained in the ideal region. It appears that the change in entropy is the major thermodynamic factor involved in the adsorption process under study. Differences in adsorption for these compounds are discussed on the basis of the electronic and steric configuration of the polar groups.

The interaction of a carcinogenic hydrocarbon, 3-methylcholanthrene, with mixed films of various mole fractions of cholesterol and lecithin was investigated. The extent of interaction between 3-methylcholanthrene and cholesterol in the mixed films is greatly influenced by the competitive interaction between cholesterol and the phospholipid. At 50:50 cholesterol—lecithin molar ratios, where these lipids interact to the greatest extent, the interaction with 3-methylcholanthrene is weakest. These competitive interactions may account for the experimental observations that phospholipids retard while cholesterol accelerates the formation of tumors induced by polycyclic aromatic hydrocarbons.

Low concentrations of poly-L-lysine, a polycationic hydrophilic molecule, caused a large expansion of polyphosphoinositide monolayers and produced a significant loss of cochlear microphonic potentials in perilymphatic perfusions in the guinea pig. In contrast, the monomeric L-lysine had only slight effects on polyphosphoinositide monolayers and did not affect cochlear microphonic potentials even at concentrations as high as 10mM. These data substantiate the hypothesis that the expansion of polyphosphoinositide monolayers by a drug is an indicator of its ototoxicity.