Seiji Sawamura

Pressure Dependence of the Solubilities of Anthracene and Phenanthrene in Water at 25°C

Solubilities of anthracene and phenanthrene in water were measured at 298.15K at pressures to 200 MPa and were found to decrease with increasing pressure.From the pressure coefficients of the solubilities, the volume changesaccompanying the dissolution were estimated to be 15.1±0.6 cm3-mol−1 for anthraceneand 12.4±0.3 cm3-mol−1 for phenanthrene. The partial molar volumes of thesesolutes in water are presumed to decrease with increasing pressure, contrary to thenegative compressibility of alkylbenzenes previously observed in water. Volumechanges accompanying hydrophobic hydration are also estimated to be 1.4cm3-mol−1 for anthracene and 4.1 cm3-mol−1 for phenanthrene, respectively. Thesepositive values are opposite to the negative ones usually observed for hydrophobichydration. The hydration structure of these hydrocarbons is discussed.

Swelling of poly(N-isopropylacrylamide) gels in water-aprotic solvent mixtures

The swelling volume of poly(N-isopropylacrylamide) (PIPAAm) gel in aprotic solvents (acetonitrile (AcN)-, tetrahydrofuran (THF)-, 1,4-dioxane (DO)- and dimethylsulfoxide (DMSO))-water mixtures was measured at 25°C. The gel swollen in water shrank first and then reswelled with addition of the aprotic solvents. At an intermediate mole fraction (XDMSO) range of DMSO-water mixtures, the gel demonstrated a “reentrant” swelling phenomenon the hydrated gel shrank first on addition of a small amount of solvent, showed a typical wide reentrant transition, and gradually reswelled in the range near pure solvent. On the other hand, the gels in AcN-, THF-, and DO-water mixtures demonstrated a “reentrant-convex” swelling phenomenon: the gels reswelled after a reentrant phase transition in low Xorg (XAcN, XTHF and XDO), showed a maximum swelling in the intermediate Xorg region, and shrank again gradually in the high Xorg region. Such a swelling behavior of the gel was interpreted by correlating with solution properties of the aqueous aprotic solvent mixtures.The strength of hydrogen bonding around amide groups of the homopolymer was examined in pure solvents (water, THF, and DMSO) and in all proportion of aqueous THF to observe the relation with swelling behavior of gel by spectrum analysis of the amide I and II bands of Fourier Transform Infrared Spectroscopy (FT-IR). The swelling properties of gels in solvents and the aqueous mixtures were well correlated with the peak shifts of amide groups of the homopolymer.

High pressure rolling‐ball viscometer of a corrosion‐resistant type

A high pressure rolling‐ball viscometer was designed for use with corrosive solutions such as electrolytes, using a glass inner cell with a glass cylinder and its piston. The viscosities of water and 2.55‐m sodium chloride aqueous solution were measured up to 375 MPa at 25 °C with an error of less than ±1%.

Effect of pressure on the solubilities of LiF, NaF, KCl, NH4, Cl, K2SO4, (NH4)2SO4, and ZnSO4·7H2O in water at 298.15 K

Abstract Solubilities of seven inorganic compounds in water were measured at 298.15 K and up to 350 MPa. The solubilities of K2SO4, LiF, NaF, and KCI increased with increasing pressure, those of NH4Cl and (NH4)2SO4 decreased, and that of ZnSO4·7H2O showed almost no dependence on pressure. From the slopes of these solubility curves at 0.1 MPa, we estimated the volume changes accompanying the dissolution of the solutes. These values coincided with the volume differences between the partial molar volume at saturation and the molar volume of the crystal within ca. ± 1 cm3 mol−.

Anomalous pressure dependence of the solubility of C60 in n-hexane

Abstract Generally, the solubility of a molecular crystal decreases with increasing pressure. However, a huge enhancement in the solubility of C 60 with increasing pressure up to 400 MPa at 298.15 K is observed in n -hexane.

Pressure-Induced Red Shift and Broadening of the Qy Absorption of Main Light-Harvesting Antennae Chlorosomes from Green Photosynthetic Bacteria and Their Dependency upon Alkyl Substituents of the Composite Bacteriochlorophylls

When pressure was applied to the main light-harvesting apparatus (chlorosomes) isolated from several green photosynthetic bacteria (up to 128 MPa), the Qy-absorption band in an aqueous solution was shifted to longer wavelengths. The shift, deltav, was completely reversible for (de)compression and also showed a linear relation as a function of the applied pressure. The pressure-sensitivity in the deltav was dependent upon the bacterial species. The pressure coefficient, deltav/deltaP, was -565 to -535 cm(-1) GPa(-1) for the chlorosomes from several green sulfur bacteria (Chlorobium species), which have several bacteriochlorophyll(BChl) homologues at the 8- and 12-positions as the antenna pigments. In contrast, a smaller value (-445 cm(-1) GPa(-1)) was estimated for the chlorosomes from the green nonsulfur bacterium (Chloroflexus aurantiacus), which has a single homologue with 8-ethyl and 12-methyl groups. These results were confirmed by the similar pressure dependency of in vitro self-aggregates of isolated BChls-c having various alkyl substituents at the 8- and 12-positions. The present pressurization study enables us to discuss a physiological meaning of a variety of antenna pigments in green photosynthetic bacteria.

NORMALIZED FLUCTUATIONS, H2O VS N-HEXANE : SITE-CORRELATED PERCOLATION

Entropy, volume and the cross fluctuations were normalized to the average volume of a coarse grain with a fixed number of molecules, within which the local and instantaneous value of interest is evaluated. Comparisons were made between liquid H2O and n‐hexane in the range from −10 °C to 120 °C and from 0.1 MPa to 500 MPa. The difference between H2O and n‐hexane in temperature and pressure dependencies of these normalized fluctuations was explained in terms of the site‐correlated percolation theory for H2O. In particular, the temperature increase was confirmed to reduce the hydrogen bond probability, while the pressure appeared to have little effect on the hydrogen bond probability. According to the Le Chatelier principle, however, the putative formation of ‘‘ice‐like’’ patches at low temperatures due to the site‐correlated percolation requirement is retarded by pressure increases. Thus, only in the limited region of low pressure (<300 MPa) and temperature (<60 °C), the fluctuating ice‐like patches are con...

High-pressure investigations of solubility

We have measured the solubilities of several inorganic and organic compounds at high pressures up to 400 MPa. For this purpose, care should be exercised in instrumentation. The results include solubility values for aqueous solutions of NaCl, NaCl.2H2O, toluene, anthracene, phenanthrene, and amino acids (Gly, Ala, Val, Leu, and Ile). In addition, we determined the solubility of C60 in n-hexane and toluene. The data for individual systems served to elucidate the mechanisms of dissolution. For example, the data for toluene, anthracene, and phenanthrene in water provided insight into hydrophobic hydration.

Volumetric Properties of Hydrophobic Hydration under High Pressure

In this article, partial molar volumes of hydrophobic compounds in water were reviewed. Distorted surfaces of the partial molar volumes for alkylbenzenes in water were drawn in a wide range of pressure, 0.10–400 MPa, and temperature, 273–323 K. They include a domain of negative compressibility of the partial molar volume in a low temperature and low pressure region. The negative compressibility was ascribed to a well‐known property of bulk water; more compressible at lower temperature in the observed region. Aromatic ring which was included in naphthalene, anthracene, etc. contribute to the positive sign of the volume change for hydrophobic hydration though the negative sign has been usually observed for a methylene group of many hydrophobic compounds.

Effects of pressure and temperature on the solubility of ammonium chloride in water

Abstract Solubility of ammonium chloride in water was measured at pressures in the range of 0.10–300MPa and temperatures in the range of 273.4–313.2K and was found to decrease with increasing press...