Abstract
Measurement of the decrease in radioactivity of a sample of BaC14O3 when exposed to an atmosphere of CO2 gas is the means used to detect exchange of CO2 between the solid and the gas. Observations are made under various atmospheric conditions with BaC14O3 prepared in various ways, and the results indicate that a small amt. of atmospheric moisture is sufficient to bring about the exchange; that above this limiting value, the rate of exchange is independent of the humidity; the amt. of exchange taking place depends on the size of the particles of BaCO3, the larger the particles, the less the exchange, indicating a surface reaction; heating the BaCO3 will make the exchange negligible.