Relationship between the transfer rate and the gap in partial pressure of gas molecules at a heterogeneous interface

The kinetic energy of a gas molecule dissolved in an aqueous solution in the stationary state is inversely proportional to its solubility according to the distribution law of kinetic energy between the gas and liquid phases. From the difference in solubility, it is deduced that the gas molecule undergoes a change in energy in the passage across a heterogeneous interface, which is countered by a difference in energy level, or a gap in partial pressure, between the two sides. In order words, unless there is the gap in partial pressure, which has hitherto been disregarded in solving the diffusion equation, it is impossible to equalize the efflux of gas molecules with the influx. The relationship between the gap in partial pressure and the transfer rate is theoretically derived from the difference in solubility. The transfer rate is evaluated by multiplying the gap size by the transfer coefficient n, which in turn is expressed by an equation containing the unique value, k, for conductivity across the interface. Comparing the theoretical and experimental transfer coefficients obtained across the gas-liquid interface, the k value at which a gas traverses the liquid side per unit difference in partial pressure is estimated to be 6.58 x 10(-3) cm.s-1.Atm-1. Gas solubility in the RBC membrane is estimated to be ca. 22% of that in water, regardless of gas type, for O2, CO, and CO2. The increase in transfer coefficient across the RBC membrane by convection is explained by an additional change in kinetic energy in extracellular fluid attributable to an external force. The reduction in the transfer coefficient in the presence of increased protein is ascribed to an increase in kinetic energy of the membrane at the RBC boundary. The solubility in the membrane is linearly related to added protein concentration.