JACQUES LOEB 43 



Our method was. the same as in our previous experiments. 1 gm. of 

 finely powdered gelatin was put into each of a series of beakers con- 

 taining 100 cc. of a solution of HCl of various concentrations (m/S to 

 m/8192). This series served as a control. We then experimented 

 with HCl solutions of different concentrations (m/8 to m/8192), each 

 containing a certain salt (e.g. Na2S04 or Ca(N03)2) in the same con- 

 centration (m/16). The gelatin remained for 30 minutes in these 

 solutions of a temperature of 20°C. The gelatin was then poured 

 into cylindrical funnels of the same diameter, to allow the acid or 

 acid-salt mixture to drain off, and the gelatin was then perfused three 

 times with 25 cc. of distilled water of 10°C., and a fourth time with 

 H2O of 20°C.^ The gelatin was then melted and made into a 1 per 

 cent solution. Dialysis experiments, titration experiments, and deter- 

 minations of pH by Sorensen and Clark's indicator method^ made it 

 probable that the solutions contained no acid except that due to hydro- 

 lytic dissociation of the gelatin salt formed ; it was also possible to show 

 that the neutral salt added to the HCl solution had been washed away. 



The following physical qualities of the washed gelatin were 

 ascertained : 



/10,000 



1. The conductivity ( — ; I, at 24 C. 



y ohms 



2. The osmotic pressure expressed in mm. height of the 1 per cent 

 gelatin solution in the manometer tube. 



3. The total swelling expressed in mm. of the height of the cylindri- 

 cal mass of gelatin. 



4. The alcohol number; i.e., the cc. of 95 per cent alcohol required 

 to precipitate 5 cc. of 1 per cent gelatin solution at 20°C.^ 



The results are given in the form of curves in which the logarithms 

 of the concentration of the acid used are the abscissa and the above 

 mentioned values for conductivity, osmotic pressure, swelling, and 

 alcohol number, the ordinates. The pH of each gelatin solution was 



^ The water was used at these temperatures to prevent excessive swelling and a 

 retardation of the process of filtration. 

 • ^ We are obliged to Dr. Dernby for demonstrating to us the use of these methods. 



* The viscosity of the solutions was determined in a special set of experiments 

 and the viscosity curves r&n parallel to those for osmotic pressure. They may 

 therefore be omitted in this paper. 



