The Influence of Protein Concentration on the Conductivity of Human Serum

A few years ago it was found ls2 that the effect of pure gelatin and crystalline egg albumin on the conductivity of a 0.6 per cent NaCl solution is dependent on the hydrogen ion concentration. Additional increments of protein increased total conductivity when the proteins were highly ionized (pH 3.3) and decreased it when they were relatively less ionized (pH 5.1 and 7.4). At the reaction of human serum (pH 7.4), where the proteins are but slightly ionized, the conductivity decreases as the concentration of serum protein increases, providing, of course, that the other electrolytes remain constant. In 1895, Sjiiqvist? in the course of a long series of experiments on the physiological chemistry of hydrochloric acid, added egg albumin in varying amounts to a 0.05 N NaCl solution, determining thereafter the conductivities of these solutions. There was very little change as the albumin percentage increased; for example, the molecular conductivity of the pure salt solution was 89.6, whereas that of the 6.3 per cent albumin solution was 89.2. It is probable that these experiments were carried on at a pH just between the point where relatively high protein ionization causes an increase of total conductivity and the lower level of ionization where the protein actually decreases conductivity.