Certain applications of the Donnan equilibrium to human blood serum

Abstract

Some months ago the authors found 1 in comparing some physical and chemical properties of serum and serous effusions that qualitatively certain definite relations obtained, regardless of the nature of the cause of the edema. Some of the relationships observed were: that the potassium content of serum is always higher than that of the effusion, the chlorine content of the serous fluid is higher than that of the serum, while sodium and HCO₃ are apparently equally distributed. It was found, furthermore, that when serum and serous fluid were separated by a collodion membrane and the system was permitted to come into equilibrium these relationships persisted. In this work it was suggested that the relationships existing between serum and serous effusion were the result of a membrane equilibrium and that the quantitative differences were apparently a function of the protein concentration.

In recent experiments we dialyzed human serum against 0.8 per cent. NaCl brought to a P_H of 7.4 by means of NaHCO₃ until the serum was practically potassium free. This dialyzed serum protein in various dilutions (made with the NaCl solution) was then dialyzed against 0.8 NaCl at a P_H of 7.4 and at equilibrium, the concentrations of Na and Cl were determined in the serum within the collodion sac and the outside fluid. It was found that [Cl] was greater in the outside fluid than in the serum and the difference was greater the higher the protein concentration in the sac. Apparently the [Na] was greater within the sac containing serum than in the surrounding fluid though the results were not conclusive, owing to considerable error in the method.