DONNAN EQUILIBRIUM AND THE PHYSICAL PROPERTIES OF PROTEINS. IV.' viscosiTY--Continued. BY JACQUES LOEB

1. In order to complete the demonstration that the viscosity of suspensions of powdered gelatin in water is influenced by electrolytes in a similar way as the viscosity of solutions of gelatin, it is necessary to prove that the characteristic valency effect exists also in the case of the viscosity of suspended particles of solid gelatin in water. This proof is furnished in Fig. 1. 0.5 gm. of finely powdered gelatin (going through a sieve of mesh size 100 but not through a sieve of mesh size 120) of pH 7.0 was put into a series of beakers containing each 100 cc. of HC1 of different pH and kept in the solution over night at a temperature of 20°C. Simultaneously a similar series of beakers containing each 100 cc. of H3P0, and H2S04 of different pH (instead of HC1) were prepared, each receiving also 0.5 gm. of powdered gelatin. After 19 hours the viscosities of all these series of suspensions were determined at 20°C. Fig. 1 gives the result, the ordinates being the values for the viscosity ratios, gelatin suspension: water, and the abscissae are the pH of the solid gelatin particles at equilibrium. The curves show that the viscosity of suspensions of gelatin sulfate is a little less than half that of suspensions of gelatin chloride and phosphate of the same pH. The curves for the suspensions of gelatin chloride and gelatin phosphate are alike, with the exception of part of the descending branch. Experiments on the influence of these three acids on swelling published in a previous paper I show that the curves for the relative volume of powdered gelatin in solutions of these three acids are similar to the