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Recent investigation has shown that ozone can be efficiently prepared by electrolysis of perchloric acid at low temperatures. Free of nitric oxide and other acid impurities, electrolytic ozone was directly obtained at concentrations above 20 weight‐per cent. Depending on cell design, the diluent gases are either oxygen or a mixture of hydrogen and oxygen. We have also found that a variable heretofore generally overlooked in current efficiency studies—the effect of reducing the absolute pressure over the electrolyte—can have a marked effect on current efficiency. Improved ozone yields are obtained at absolute pressures of 0.1 atmosphere. With cells of the type reported herein, eutectic mixtures of perchloric acid and water give excellent results at temperatures below −50°C. Sodium and magnesium perchlorates may be added to perchloric acid solution to give slightly lower melting points, with indication of some increase in current efficiency. Provided a partially frozen electrolyte is used, current efficiency does not vary appreciably over a wide current density range. Smooth platinum is a satisfactory anode material and silver‐free lead is suitable for the cathode. The consumption of platinum is known to be less—probably much less—than 10 milligrams per kilogram of ozone. The combined mechanical and chemical losses of perchloric acid are less than 1.7 grams per kilogram of ozone. For the direct preparation of relatively pure Ozone at high concentrations, the process described is more efficient than the silent electric discharge method.

Critical flow of two-phase steam-water mixtures in annuli has been studied, with a cylindrical test section 0.574 in. in diameter with an axially centered rod, 0.187 or 0.375 in. O.D., as a pressure probe. Pressure taps on the wall and the center rod permitted an accurate determination of the pressure profile over the entire length of the section, and, in cases where a movable probe was used, a short distance into the downstream exhaust chamber. Results were correlated by plotting the ratio of the observed critical mass velocity to the theoretical critical mass velocity for homogeneous flow as a function of quality.Exit pressures were found to be lower than most values previously reported. The ratio GJGTH was found to be independent of the probe diameter, the manner of upstream steam-water mixing, and, for test sections greater than 9 in. in length, the test section length. Since probe diameter had no observable effect on GJGTB, the correlation may be applicable to full bore pipes near % in. in diameter. In the range of qualities from 2 to 15% the critical G,,/GTx ratio was depressed with increasing exit (throat) pressure, but a t other qualities no pressure dependency was noted. The effect of changing the downstream exhaust chamber pressure was found to influence the exit pressure but to have little effect on the observed critical mass velocity.

W a s h i n g t a n A unified theory of one-dimensional, adiabatic, separated, two-phase flow is presented. T o describe the flow adequately, four mixture specific volumes are defined. They are based on area, momentum, kinetic energy, and velocity averages. Increasing relative velocity between the phases initially lowers a l l mixture specific volumes except the velocity average. The momentum average specific volume minimizes when the slip ratio equals (V,/Vf)'/Z, while the kinetic energy average specific volume reaches i t s minimum value a t a slip ratio of (Vg/Vf)1'3. Area average specific value does not minimize with slip ratio.Because a higher slip ratio would decrease the entropy of a closed system, ( V g / V f ) 1 / 3 is the maximum slip ratio attainable in two-phase critical flow. Based on the maximum slip ratio and isentropic flow, a new critical flow model was developed and compared with the steam-water critical flow data of four recent investigations. While the predicted flow rates followed well the pressure behavior of the experimental data, they were too low a t high qualities and too high a t low qualities. The average percentage difference between experimental and predicted critical flow rates was -8.5% (three hundred and seventy-six data points).Differences i n the approach to critical flow between a gas and a vapor-liquid stream appear to be caused by the latter's increased frictional and gravitational pressure drops and relative velocity effects.

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Oxygen overvoltage was measured on platinum electrodes in 5M perchloric acid from -45 ~ to +40~ and in 0.005-9M perchloric acid at 0~ A limiting current density that was found is due to activation overvoltage at the anode surface. This limiting current density decreased at lower temperatures and in higher perchloric acid concentrations. It also marked the beginning of ozone formation. Adsorption of perchlorate ions is bebelieved to be the cause of the limiting current density.

x) -(xo) for the tubular reactor(x-) ( y ) ! I = vector of mole fractions in the reservoir a t z = = (x) -(x') for the nonflow diffusion tube or = mole fraction integrated over tube length tor) = axial coordinate, dimensionless -" u = z " / L (nonflow) or z"DR/VmR2 (tubular reacz" = axial coordinate, cm. Greek Letters ff = x--X f t e x = eigenvalue wP n, LITERATURE CITED = radial position in tubular reactor, dimensionless = t DR/L2 = time, dimensionless = defined by Equation ( 4 b ) = defined by Equation (4a) 1. Bak, Thor A,, "Contributions to the Theory of ChemicalThc nature of flaw choking has been studied as steam-water mixtures are passed through a tube with ever increasing pressure gradient. Choked flow for two-phase, one-component mixtures has been characterized with a separated flow model as resulting from maximization of the ratio of gas to liquid velocities, or slip ratio. Slip ratios at choking were measured and found to increase from 1.2 to 5.0 at 30 Ib./sq.in. exit plane pressure with decrease in quality from 0.95 to 0.02. Separated models predict either 9.3 or 28.4 with no quality dependence. The difference i s attributed to liquid entrainment. Flow regimes were observed to vary from purely entrained t o annular entrained to slug entrained as quality decreased. Normal shock waves were observed in the free jet at qualities obove 0.25. Choking flow rates were predicted with an average error of less than 2% with a stagnation energy balance model using an empirically developed slip ratio relation corrected far entrainment.High-velocity flow of vapor-liquid mixtures through ducts is characterized by ill-defined interfaces between phases and momentum and thermal relaxation times sufficiently long to result in nonequilibrium flow. Improved characterization of such a complex flow system has been the goal of researchers working in such diverse fields as oil reservoir recovery, rocket engine design, and nuclear reactor cooling. Of particular interest has been the prediction of choking conditions under which further increases in flow rate through a duct cannot be produced by decreasing downstream pressure.Historically, choking, or critical flow, in a two-phase system was first analyzed by assuming that the two phases W. 1. Klingebiel is with Union Carbide, Bound Brook, New Jersey.