Netsu Sokutei

The inhibitory effect of some polyols which are added in various cosmetics and toiletries as humectants, emulsion stabilizers and for some other purposes against the growth activity of Escherichia coli in liquid media was studied by a calorimetric technique. The polyols studied were 1, 2-ethanediol (ethylene glycol), 1, 2-propanediol (propylene glycol), 1, 2-butanediol (1, 2-butylene glycol), 1, 3-butanediol (1, 3-butylene glycol), 1, 2, 3-propanetiol (glycerol), 1, 2-pentanediol (1, 2-hydroxypentane), 3-(3-hydoxypropanoxy) propan-1-ol (di(propylene glycol)) and polyethylene glycol. The growth thermograms observed in the absence and the presence of increasing amounts of the polyols were analyzed to determine the inhibitory parameters, the polyol concentration which inhibits the growth of the microbes by 50% (K_μ or K_θ) and the concentration which completely prevents the growth (MIC_μ or MIC_θ). All of the polyols studied were found to exert the inhibitory effect with the 50% inhibitory concentrations between 1∼17% (W/V) for E. coli. It was also shown that the apparent affinity of the polyols to the microbial cell calculated on the basis of the Gibbs equation linearly increases with the length of their alkyl chains, indicating that the inhibitory effect of the polyols is related to their hydrophobicity.

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The adsorption phenomena taking place on the powdered solid surfaces have been elucidated by the measurement of heat of adsorption and the spectroscopic observation. As to the interaction between the metal-oxide surface and water molecules, metal oxides exhibit either an energetically homogeneous nature or heterogeneous nature; ZnO, Cr₂O₃, and SnO₂ belong to the former type, and TiO₂, ZrO₂, Al₂O₃, and SiO₂ to the latter type. Two-dimensional condensation of water occurs on the hydroxylated surfaces of ZnO, Cr₂O₃, and SrF₂, which is due to the strong and lateral interaction of water molecules adsorbed on the homogeneous solid surface. In this review the peculiar adsorption found in the zeolite-dinitrogen system is also described and the process of investigating its mechanism is introduced by showing the data of adsorption heat and spectroscopic observation such as IR, XAFS (including EXAFS and XANES), and emission spectra. The copper ion species ion-exchanged in mordenite or CuZSM-5-type zeolite act as effective sites for dinitrogen adsorption at room temperature. The monovalent copper ion species (Cu⁺) that produced by the heat treatment at high temperature in vacuo is responsible for the strong adsorption of dinitrogen. Usefulness of combining the adsorption calorimetry and spectroscopic observation is also described in this review.

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