JACQUES LOEB 107 



a gelatin solution from water by a collodion membrane we get two 

 equilibria, one across the membrane caused by the protein ions on 

 one side of the membrane ; and a second one inside the protein solution 

 caused by the solid particles of jelly. 



2. These experiments in which liquid gelatin was replaced by 

 solid particles of gelatin support the idea of a reciprocal relation 

 between the osmotic pressure and the viscosity of gelatin solutions. 

 It is, however, possible to give a more direct proof. It was noticed 

 that the viscosity of solutions of gelatin chloride does not always 

 increase on standing but that it diminishes when the temperature 

 exceeds a certain limit. This is shown for a 2 per cent solution of 

 gelatin chloride of pH 2.7 in Fig. 6. The viscosity of such a solution 

 increases on standing very rapidly at 15°C., much less rapidly at 

 25°C., but diminishes when kept at a temperature above 35°C., 

 and the more rapidly the higher the temperature. This we assume 

 to be due to the fact that at a temperature above 35° the rate of 

 melting of submicroscopic particles of solid jelly exceeds the rate 

 of their formation from isolated ions or molecules. 



Several liters of a 0.55 per cent solution of isoelectric gelatin were 

 kept at about 10°C. for 48 hours and at 20° for the next 24 hours. 

 Then the stock solution was divided into two parts. The one part 

 was divided into parts of 90 cc. each, and each part was brought to 

 different pH by adding 10 cc. containing different quantities of HCl. 

 In this way the concentration of originally isoelectric gelatin was, 

 therefore, in every case 0.5 per cent. The second portion was treated 

 in the same way except that before adding the acid the gelatin was 

 kept for 1 hour at 45°C. This was done to melt part of the submicro- 

 scopic pieces of jelly assumed to exist in the solution and thus to 

 increase the concentration of the isolated ions and molecules and to 

 diminish the relative quantity of solid submicroscopic particles capable 

 of occluding water and thereby causing the high viscosity character- 

 istic of gelatin solutions. After this second portion of the stock 

 solution of isoelectric gelatin had been kept for 1 hour at 45°C. it was 

 rapidly cooled to 20°, the HCl was added in the way described for 

 the first portion and the solutions were put into collodion bags to 

 measure the osmotic pressure. Each collodion bag contained about 

 50 cc. of gelatin solution. The temperature now remained constant 



