The Equilibrium between Varying Concentrations of Acids and Alkalies and the Proteins of the Serum and other Colloids, with a Discussion of the Nature of Colloidal Reaction or Adsorption.

It was shown by Moore and Wilson' in 1906 that the serum proteins possess a relatively enormous power of taking up acid or alkali within narrow ratios of hydrogen and hydroxyl ionic concentration. Thus serum titrated with alkali to the neutral point to phenol-phthal6in, and then to the neutral point to an indicator such as 'di-methyl' or methyl orange, shows a difference indicating no less a concentration than 0-14 to 016 Normal. Outside these two limits of neutrality to the two coloured indicators the hydrogen or hydroxyl ion concentration swings up very rapidly compared to the rate of change within the limits. We may hence speak of a ' neutral zone ' for the protein of the serum. The traverse of this zone amounts to about 0-15 N, and within this zone the reaction is nearly neutral. Outside of it in either direction the acidity in the one case or alkalinity in the other mounts very rapidly. Moore and Wilson drew attention to the curious and interesting fact, that this concentration in regard to acid or alkali of the proteins amounts to about an isotonicity with the entire inorganic salts of the serum. The tonicity for all mammalian sera is very nearly constant. amounting to about that of a 0 9 per cent. solution of sodium chloride, that is to say to about 0-15 N; this close coincidence can scarcely be fortuitous, and would support the view that the figure 0-15 N indicates an average reactivity of the serum to crystalloids, and shows that under normal conditions the amounts of crystalloids in the serum are regulated by the combining or adsorbing powers of the serum colloids.2