Measurement and regulation of oxygen content in selected gases using solid electrolyte cells. IV. Accurate preparation of CO2-CO and H2O-H2 mixtures

Abstract

Mixtures of CO2-CO, H2O-H2 and Ar-H2O-H2 of precise composition were prepared using a zirconia pump and analysed with a zirconia gauge. The\(P_{{\text{CO}}_{\text{2}} } /P_{{\text{CO}}}\) ratio was varied from 5×10−2 to 104 and the\(P_{{\text{H}}_{\text{2}} {\text{O}}} /P_{{\text{H}}_{\text{2}} }\) ratio from 3×10−4 to 10−2. A ‘Faraday's Law test’ proved to be a simple and reliable procedure for checking the conditions of utilization of these gaseous mixtures and for verifying that no significant disproportionation of CO or leakage along the gas circuit altered the prepared composition. From a practical point of view the best methods of preparing mixtures with low oxygen activity are reduction of carbon dioxide in the range 5×10−11 to 10−17 atm and oxidation of inert gas-H2 in the range 10−19 to 10−27 atm at 800°C.