DONNAN EQUILIBRIUM AND THE PHYSICAL PROPERTIES 



OF PROTEINS. 



IV. VISCOSITY — Continued. 



By JACQUES LOEB. 

 {From the Laboratories of The Rockefeller Institute for Medical Research.) 



(Received for publication, July 14, 1921.) 



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 contain- 

 ing each 100 cc. of HCl 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 H3PO4 and H2SO4 of different pH 

 (instead of HCl) 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 abscissa; 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 suspen- 

 sions 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 pub- 

 lished in a previous paper^ show that the curves for the relative volume 

 of powdered gelatin in solutions of these three acids are similar to the 



» Loeb, J., /. Gen. Physiol, 1920-21, iii, 253. 



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