Surface conductance measurements of adsorbed gases

The surface conductance of adsorbed water, carbon dioxide, and ammonia has been measured as a function of temperature using a triple-track test substrate. The individual pure gases were studied along with their mixtures. Adsorbed carbon dioxide or ammonia was found to have a negligible surface conductance, while adsorbed water exhibited an increase in conductance beginning at -25°C. Mixtures of carbon dioxide and water exhibited essentially the same conductance as water by itself, while mixtures of ammonia and water exhibited a conductance 10 ⁴ times larger than water between -40°C and 0°C. Mixtures of all three gases resulted in a relatively low conductance at lower temperatures (-100°C to -50°C). Corresponding pressure measurements indicated that vaporization was greatly suppressed in some cases, suggesting strong interaction between the adsorbed species