A manostat volumetric apparatus for studies on the kinetics of high-temperature reactions in solid-gas systems

Abstract

A new volumetric apparatus is described for continuous measurement of the kinetics of the oxidation of metals at high temperatures, and for measurement of adsorption and chemisorption of gases on solids. The measurement of the kinetics of oxygen fixation is performed automatically with very high precision. The oxidation of copper has been used to test the performance of the apparatus.Studies on the mechanisms of reactions in solid-gas systems, which include such processes as the thermal decomposition of solids and oxidation of metals and alloys, require the use of increasingly accurate methods of measurement [1,2].Kinetic measurements pray an essential role in these studies. In the case of oxidation processes, for instance, these measurements at various temperatures and pressures of the oxidizing medium provide valuable information about elementary processes which, under the given conditions, control the rate of the overall reaction. In many cases they allow calculations to be made of the defect concentration and self-diffusion coefficient of a metal or an oxidant in the solid product of oxidation of a metal or an alloy.Of the numerous methods used for studying the kinetics of the processes under discussion, two basic methods may be distinguished: a gravimetric and a volumetric method, which provide the most accurate results.In the present paper a new volumetric apparatus is described which makes it possible to obtain very accurate values of the rate constants of reactions in the given temperature and oxygen pressure ranges. Description of the apparatusDue to application of a new system of manostats, the apparatus to be described enables measurements of the volume of gas consumed by a sample under isothermal-isobaric conditions to be made with high precision. All operations involved in the measurement of the reaction kinetics, with the exception of the reading of a mercury level in the measurement burette, are automatic. The range of pressures of the apparatus used in the present work was 2-600 mm Hg. It will be possible in the future to extend this range by modifying the apparatus. The work on such a modification is now in progress.