TRANSPORT OF CARBON-DIOXIDE BETWEEN THE GAS-PHASE AND WATER UNDER WELL-STIRRED CONDITIONS - RATE CONSTANTS AND MASS ACCOMMODATION COEFFICIENTS

The rate constant for absorption of carbon dioxide into water increase s as the stirring rate of the water is increased up to a maximum rate and then stays constant until the stirring is sufficiently vigorous to affect the surface area. At the maximum, the change in absorption rat e with gas pressure shows excellent first-order kinetics and can be in terpreted in terms of reversible exchange between the gas phase and a uniform solution, without invoking the existence of a surface layer of saturated solution, A general treatment is described for extracting t he rate constant for absorption of gas from the kinetic data. By compa ring the rate of absorption with the rate predicted by kinetic theory, we obtain an accommodation coefficient (gamma) of(5.5 +/- 0.5) x 10(- 8) at 20 degrees C. Absorption rates measured in solutions of sodium c hloride decrease with increasing ionic strength. We note an approximat ely linear relationship between log gamma and log s, where s is the ga s solubility at 1 atm.