Toshiharu Takagi

Ultrasonic speeds and thermodynamics for binary solutions of n-alkanes under high pressures

Abstract Ultrasonic speeds and densities for binary solutions of n-alkanes: [n-hexane+n-decane] , [n-octane+n-dodecane] and [n-decane+n-tetradecane] were measured at 298.15 K under pressures up to the freezing line or 100 MPa. These results are used to calculate the thermodynamic properties. An examination of these quantities offers powerful clues to the understanding of the character of binary solutions under high pressure.

Solubilization of ionic dyes in supercritical carbon dioxide: a basic study for dyeing fiber in non-aqueous media

Solubilization of ionic dyes in supercntical carbon dioxide has been investigated using the reverse micellar system. The reverse micelle composed of pentaethylene glycol n-octyl ether and co-surfactant provided suitable solubilizing space for ionic dyes in supercritical carbon dioxide. The effect of the co-surfactant, alcohol, on the stability of the reverse micelle was also investigated. It was found that stability of the reverse micelle and capacities to dissolve water and ionic dyes in the system are greatly dependent on the chain length of alcohol.

Ultrasonic speeds and thermodynamics of (benzene + aniline) and (chlorobenzene + aniline) under high pressures

Abstract Ultrasonic speeds in (benzene + aniline) and (chlorobenzene + aniline) were measured by a fixed-path pulse technique at 298.15 K under pressures up to that of freezing or 210 MPa. Densities were calculated from these results using the pressure dependence of the ultrasonic speeds of the mixtures. The densities thus obtained agreed well (to within approximately 0.2 per cent) with experimental values reported in the literature over the whole experimental pressure range. Combining the values obtained for ultrasonic speed with the calculated densities, the isentropic and isothermal compressibilities at high pressures have been derived with reasonable accuracy.

Ultrasonic speeds and thermodynamics of (benzene+an isomeric xylene) under high pressures

Ultrasonic speeds in (benzene + m-xylene) and (benzene + p-xylene) were measured by a fixed-path pulse technique at 303.15 K under pressures up to that of freezing or 200 MPa. The accurate isentropic compressibilities for (benzene + an isomeric xylene) including (benzene + o-xylene) have been determined from the experimental results and densities estimated using the pressure dependence of ultrasonic speed. The present excess isentropic compressibilities are positive for all compositions and pressures, and when the values at x = 0.5 are plotted against pressure, the curve for (benzene + p-xylene) exhibits a smaller pressure dependence than that for (benzene + o-xylene) or (benzene + m-xylene).

Ultrasonic speeds and thermodynamic properties of (benzene + chlorobenzene) and (benzene + bromobenzene) under high pressures

Abstract Ultrasonic speeds in (benzene + chlorobenzene) and (benzene + bromobenzene) were measured by a fixed-path pulse technique at 303.15 K under pressures up to that of freezing or 200 MPa. Densities under high pressures were calculated from experimental results with reasonable accuracy by use of the pressure dependence of the ultrasonic speed. These values have been used to obtain the excess isentropic compressibility. The values of the present excess isentropic compressibilities of both binary mixtures are negative for all compositions at the experimental pressures, and show similar pressure variations.

Bubble point pressure for binary mixtures of difluoromethane with pentafluoroethane and 1,1,1,2-tetrafluoroethane

Abstract Bubble point pressures for the two binary hydrofluorocarbon mixtures difluoromethane, CH2F2 with pentafluoroethane CHF2CF3 and 1,1,1,2-tetrafluoroethane CF3CH2F were measured using an acoustic absorption technique. Results cover the temperature range from 243 K to 333 K with an uncertainty of ±20 kPa except at 333.15 K. For the (1−x) CH2F2+xCHF2CF3 system, bubble point pressures show a maximum around x=0.2 at 248.15 K, corresponding to the azeotropic mixture. This point shifts to the CH2F2-rich region with increasing temperature, and finally vanishes out at temperatures higher than 313.15 K. Bubble pressures for the (1−x) CH2F2+xCF3CH2F system decrease monotonously with increasing composition of CF3CH2F at each temperature. These experimental data were fairly well correlated with the Peng–Robinson equation of state including the azeotropic point.

Ultrasonic speeds and thermodynamics for (toluene + o-xylene) and (toluene + aniline) under high pressures

The ultrasonic speeds in {(1 − x)C6H5CH3 + xo-C4H4(CH3)2} and {(1 − x)C6H5CH3 + xC6H5NH2} were measured by a pulse technique of fixed-path type at a frequency of 1 MHz. The measurements were carried out over the range of pressures up to 180 MPa at 303.15 K. From the experimental results, the excess isentropic compressibilities κSE were derived at several pressures.The densities under high pressures required to calculate κSE, were estimated from the pressure dependences of the observed ultrasonic speeds. κSE for the first mixture shifts from a small positive value at atmospheric pressure to a negative value with increasing pressure, while that for the second mixture exhibits the reverse behaviour.

Ultrasonic speeds and thermodynamic properties for pentafluoropropyl alcohol, tetrafluoropropyl alcohol and trifluoroethyl alcohol under high pressures

Abstract The ultrasonic speeds u in pentafluoropropyl alcohol 5FP, tetrafluoropropyl alcohol 4FP and trifluoroethyl alcohol 3FE were measured by a sing-around technique operated at a frequency of 2 MHz. The measurements were carried out in the ranges of temperature from 283–348 K and pressure up to about 70 MPa with an uncertainty within ± 0.2%. The results for these compounds show lower absolute u values and smaller pressure dependence than those for primary alcohols. Among the compounds studied, the u values for 4FP differ greatly in their pressure effect from those for 5FP and 3FE. The relationship between 1/u(∂u/∂p)T and isothermal compressibility kt for these alcohols is fitted well by a straight line having a slope of 5 ± 0.2, as well as those for other alcohols; this slope is distinguishable from that of 4 ± 0.15 for other hydrogen compounds reported elsewhere.

Ultrasonic speed in compressed liquid by a sing-around method

Abstract A new apparatus for the measurement of ultrasonic speed in compressed liquid was constructed. The reliability of this instrument was confirmed by measuring the speeds in pure benzene in the ranges from 283.15 to 323.15 K and pressures up to near freezing pressure, and by comparing the results with literature values. The isentropic compressibilities κ S were also determined using the experimental speeds and densities, and the results κ S ( u ) were compared with those observed directly elsewhere κ S (d) and those calculated thermodynamically κ S (c) from ( p , V m , T ). At atmospheric pressure, the present results, while agreeing with κ S ( u ) reported in the literature, show differences from κ S (d) and κ S (c), while those for higher pressures close on a simple curve with κ S (c).

Ultrasonic speeds and thermodynamics for (chlorobenzene+bromobenzene) under high pressures

Ultrasonic speeds in {(1 − x)C6H5Cl + xC6H5Br} were measured by a pulse method employing 1 MHz at 303.15 K under pressures up to 200 MPa. Densities under high pressure were calculated from experimental results with reasonable accuracy by use of the pressure dependency of the ultrasonic speed. From these values, the excess isentropic compressibility was derived. The results showed small positive values under the experimental conditions. When pressure was raised, the values at x = 0.5 decreased greatly at first, and those for the higher-pressure region were found to remain nearly constant.