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HARRY TANIGUCHI AND GEORGE J. JANZ
1.14 X 10'' molecules per second. Dividing by the geometric surface area of 6.94sq. cm. gives RT exptl = 16 X 10l6molecules of CO/sq. cm.-sec.
Thus the calculated rate is in good agreement with the experimental rate. We are now in a position to understand the wide differences in data on graphite oxiddtion in the literature. Impurities in graphitic materials result in a wide variety of low activation energies being observed. The appearance of pore diffusion effects, which are influenced by particle size and porosity, results in the possibility of observing an activation energy anywhere between the value for the plane surface reaction and one-half of that value. Since impurities may change the rate controlling step in the reaction they may also change the observed order of the reaction. A surface reaction of order n will result in an observed order of n 1/2 if the surface reaction is controlled by pore
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diffusion. In this study the true surface reaction of graphite with oxygen has been found to be zero order with an 80 kcal./mole activation energy. On samples thicker than 0.1 mm., the diffusion of oxygen into the pores in the graphite results in an observed one-half order reaction with a 42 kcal. per mole activation energy. In the previous studies no successful precautions were taken to prevent the secondary reaction of carbon monoxide being oxidived to carbon dioxide. This resulted in the confusion over whether carbon monoxide or carbon dioxide or both are primary products. By the use of a very fast flow rate of oxygen past the sample this study has unequivocally shown carbon monoxide to be the primary product from 600 to 800". Acknowledgment.-The authors gratefully acknowledge the California Research Corporation for a fellowship which supported G. B. during much of this work and the U. 5. Air Force for support under contract no. AF 33(038)20839.
THE THERMODYNAMICS OF HYDROGEN CHLORIDE I N ETHYL ALCOHOL FROM ELECTROMOTlVE FORCE MEASUREMENTS' BYHARRY TANIGUCHI AND GEORGE J. JANZ Department of Chemistry, Rensselaer PolytechnicInstilute Received January 84, 1867
Electromotive force measurements of the cell without li uid junction: Pt, Hn(1 atm.) lHCl in Ethanol (m) I AgCl-Ag have been carried out at 25' over a concentration rangelrorn 0.0048 to 0.12 molal. New experimental techniques wera devised and the best t(heoretica1 treatment was employed. The standard molal electrode potential of the silver, silver chloride electrode in anhydrous ethanol is -0.08138 volt. This value and the activity coefficients of hydrogen chloride computed from the data are repommended for the practical standardization of the silver-silver chloride electrode in anhydrous ethanol at 25'.
Introduction In contrabt to the number of measurements of the activity coefficicnts of hydrogen chloride in mater-et
