Masaji Miura

Acoustic study on the kinetics for the dissociation-recombination reaction between micelle and counterion in sodium dodecyl sulfate solution

Abstract The ultrasonic absorption of sodium dodecyl sulfate (SDS) in aqueous solution was measured at 30°C. in the range of frequency between 70 kc. and 95 Mc. and of concentration from 6.5 to 100 mM. The excess absorption was observed only in the solutions the concentration of which was higher than the critical micellar concentration. The excess absorption of sound and the relaxation frequencies obtained from the absorption curves show a discontinuity with the variation of the concentration of SDS in the neighborhood of 50 mM. Other properties like viscosity, conductivity, and velocity of sound also exhibit such a change near the same concentration. It is concluded that a change in the properties of the micelles of SDS occurs in the neighborhood of this concentration. The mechanism of the observed ultrasonic absorption is considered and attributed to the reaction M″ ⇌ M′ + 2Na+, where M′ and M″ are two types of micelles. The rate constants of the forward and backward reactions are found to be 1.5 × 105 sec.−1 and 8.4 × 109 mole−2 sec.−1, respectively, and the partial molal volume change between the initial and final states in the reaction is 29.4 cm.3 mole−1.

E.S.R. spectra of PF4 radicals produced in a single crystal of PF3

E.S.R. spectra of PF4 radicals were investigated with single crystals of PF3 made at a low temperature and irradiated with γ-rays. The angular dependence of the spectral lines was satisfactorily analysed in terms of the second-order equations for large couplings of one 31P nucleus and two magnetically equivalent 19F nuclei and of the first-order equation for two 19F nuclei with small couplings. We conclude that the two magnetically equivalent fluorine nuclei occupy the axial positions of the trigonal bipyramidal structure of the PF4 radical and the other two fluorine nuclei are in the equatorial positions. Furthermore, the unpaired electron of the PF4 radical was shown to occupy an orbital consisting mainly of the 2p orbital of each of the two axial fluorine atoms along the F-P-F axis and the 3s and 3p orbitals, directed towards the vacant equatorial position of the central phosphorus atom. The orbital of the unpaired electron can be reasonably represented as a Rundle three-centre non-bonding orbital. The...

Acoustic study of the kinetics of the dissociation-recombination reaction between micelle and counterion in solutions of sodium salts of fatty acids—sodium caprylate and sodium caprate

Abstract The ultrasonic absorption has been measured in aqueous solutions of sodium caprylate and sodium caprate at 30°C over the frequency range of 5–95 mc. As in the case of sodium dodecyl sulfate, the excess absorption was observed only in solutions in which the concentration was higher than the critical micellar concentration (CMC), both in the presence and absence of salt. The mechanism for these features was attributed to the reaction M ″→M′ + 3 N a + for sodium caprylate and M ″→M′ + 2.5 N a + for sodium caprate, where M′ and M″ are two types of micelle. The rate constants of the forward and backward reactions were 3.8 × 107 sec−1, 3.3 × 109 mole−3 sec−1 for sodium caprylate and 1.1 × 107 sec−1, 2.8 × 109 mole−2.5 sec−1 for sodium caprate, respectively. Some kinetic characteristics including the free energy, enthalpy, and entropy were calculated.

Studies of the surface of titanium dioxide: II. The effect of reduction by hydrogen on the weight and the magnetic susceptibility

Abstract Simultaneous measurements of weight and magnetic susceptibility of several kinds of titanium dioxide have been carried out after an introduction of hydrogen at temperatures between 400 and 550 °C and at pressures between 0.01 and 0.5 atm. The weight of titanium dioxide decreased gradually, while the magnetic susceptibility increased, when hydrogen was introduced above 400 °C. It was found that the rate of reduction obeys partly the Elovich equation and that the weight decrease per unit weight of the sample tends to increase with an increase in the specific surface area. It could not be revealed definitely whether the crystal structure of titanium dioxide, rutile or anatase, affects the behavior of the reduction. The activation energy increased gradually with the reduced amount. The magnetic susceptibility increased linearly with a decrease in the weight. These results support the previous findings of the hydrogen reduction of titanium dioxide in connection with the anatase-rutile transformation performed by Shannon. On the basis of these results, the reduction mechanism was discussed and the rate-determining step in the initial stage was presumed to be formation of the surface hydroxyl groups followed by rapid removal of water molecules from the surface.

Ultrasonic Absorption in Sodium Metaborate Solution

The kinetics of reaction in the dilute aqueous solution of sodium metaborate have been studied by ultrasonic absorption measurements over the frequency range from 50 kc/sec to 75 Mc/sec. Single relaxation frequencies have been observed in 0.05, 0.1, and 0.2M at 25°C and in 0.1M at 35°C, and the absorption mechanism has been assigned to be due to the hydrolysis of metaborate ion. The corresponding forward and backward rate constants calculated for the reaction BO2−+H2O⇌HBO2+OH− are 4.11×103 sec−1 and 2.36×108M−1 sec−1 at 25°C for 0.05M solution, respectively. From the magnitude of the relaxational acoustic absorption per wavelength, the partial molal volume change ΔV° for the process is calculated to be 6.83 cm3/mole at 25°C for the 0.05M solution. The temperature dependence of the relaxation frequency indicates that the energies of activation for the reaction are 12.6 and 1.31 kcal/mole for the forward and backward reactions, respectively.

Ultrasonic Investigation on Kinetics of Ionic Reaction in Sodium Phosphate Solution

The velocity of sound in sodium phosphate solutions has been studied in the frequency range 2.5–6.5 Mc/sec at concentrations varying from 0.01 to 0.25M. The normal dispersion below 0.1M and the abnormal dispersion above 0.11M have been observed. In the former concentration region the dependence of concentration on the relaxation frequency gave the equilibrium constant which was in excellent agreement with that of the hydrolysis of PO43− and made clear the mechanism responsible for dispersion. The corresponding forward and reverse rate constants were calculated using the relaxation time in solution and the dissociation constants of the acid and water at 25°—35°C. The activation energy was also calculated from the temperature dependence of rate constants. The discussion was extended to the effect of dielectric constant and hydrogen‐ion concentration on the dispersion.

Studies of the surface of titanium dioxide. IV. The hydrogen-deuterium equilibration reaction

The interaction of hydrogen with the surface of titanium dioxide has been studied in connection with the hydrogen-reduction mechanism of titanium dioxide, by means of such measurements as weight decrease, magnetic susceptibility, hydrogen uptake, and electrical conductance. It was postulated in the previous study that the rate-determining step of the hydrogen-reduction reaction may be the formation of surface hydroxyl groups, followed by the rapid removal of water molecules from the surface. In this study, the interactions between hydrogen and the surface of titanium dioxide were investigated by measuring the hydrogen-deuterium equilibration reaction, H/sub 2/ + D/sub 2/ = 2HD, at temperatures above 200/sup 0/C on both surfaces before and after hydrogen reduction to compare the differences in the reactivities.