The determination of diffusion coefficients of moderately soluble gases in liquids

摘要

A rapid method of determining the diffusion coefficients of sparingly soluble gases in liquids with an accuracy of about 1% is described. The technique consists of measuring the rate of absorption of the gas in a laminar jet of the liquid, and by maintaining a constant liquid flow rate the entry and end effects are reduced to minimum significance. Diffusion coefficients of carbon dioxide in water over a range of temperatures from 18.5 °C to 75.1 °C, and of nitrous oxide in water and glycerol-water solutions at 20°C are determined. Where comparison is possible the results compare favourably with those of previous workers using other methods. The jet has also been used to determine values of c*√D for the carbon dioxide - monoethanolamine system over a range of amine concentrations from 0.988 to 4.738 moles/litre and an attempt has been made to estimate the "physical" solubility c* and the diffusion coefficient D from these values. A new interferometric method utilizing birefringence for determining gaseous diffusion coefficients directly from the gas to the liquid phase is introduced. This has the important advantage of a truly stagnant liquid surface, and a knowledge of gas solubilities is not required. The determination of the diffusion coefficient of carbon dioxide in water at 20 °C is described, and suggestions are made for improving the apparatus and for its application in a modified form to other spheres of gas-liquid mass-transfer.