92 ION SERIES AND PROTEINS. I 



pH and with the same concentration of originally isoelectric gelatin 

 all mixtures of acid and gelatin solution must have the same concen- 

 tration of gelatin-acid salt; and if this is the case they must all have 

 the same osmotic pressure if the valency of the anion is the same, 

 since the osmotic pressure is almost entirely determined by the gela- 

 tin-acid salt, that of the isoelectric gelatin being very low. This 

 conclusion is in harmony with the view expressed by Laqueur and 

 Sackur, Pauli, and others. The writer differs from Pauli only in 

 regard to the statement that the different acids, e.g. HCl, H3PO4, 

 tartaric, acetic, and trichloracetic, have different effects on the physi- 

 cal properties of proteins. 



///. Combining Ratios of Acids and Alkalies with Crystalline Egg 

 Albumin and the Osmotic Pressure of the Albumin Solutions, 



Crystalhne egg albumin was prepared under Dr. Northrop's super- 

 vision according to Sorensen's method, *° and crystallized three times. 

 The only difference in procedure was in the dialysis. Instead of put- 

 ting the water under negative pressure as was done by Sorensen, pres- 

 sure was put on the egg albumin by attaching a long glass tube full of 

 water to the dialyzing bag so that the solution was under about 150 

 cm. water pressure during dialysis. This was necessary to avoid too 

 great an increase in volume. The same stock solution of albumin 

 served for all the experiments and was diluted before the experiment 

 to a 1 per cent solution. The concentration of ammonium sulfate left 

 in the solution was between m/1,000 and m/2,000. The pH of the 

 stock solution was about 5.20. By adding about 1 cc. of 0.1 N HCl 

 to 100 cc. of a 1 per cent solution of this albumin the solution was 

 brought to the isoelectric point of the egg albumin, which is according 

 to Sorensen at pH = 4.8. 



The 1 per cent solutions were made up with different quantities of 

 acid (or alkaU) and the pH of the albumin solution was determined 

 electrometrically.^^ In Fig. 3 are plotted the curves in which the pH 

 are the abscissae and the cc. of 0.1 n acid required to obtain the various 



^" Sorensen, S. P. L., Compt. rend. trav. Lab. Carlsherg, 1915-17, xii, 1. 

 ^^ The colorimetric determination which gives fairly good results in the case of 

 gelatin is unreliable in the case of egg albumin. 



