CORRECTNESS OF THE CHEMICAL VIEWPOINT 45 



adding about 1 c.c. 0.1 N HC1 to 100 c.c. 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 S0rensen at pH = 4.8. 



The 1 per cent solutions were made up with different quantities 

 of acid (or alkali) and the pH of the albumin solution was 

 determined electrometrically. In Fig. 4 are plotted the titration 

 curves in which the pH are the abscissae while the ordinates are 

 the cubic centimeters of 0.1 N acid required to bring the 1 per 

 cent solutions of originally isoelectric crystalline egg albumin to 

 different pH. The curves represent these titration values for 

 four acids, HC1, H 2 SO4, H 3 PO4, and oxalic acid. Beginning 

 with the lowest curve, we notice that the curve is the same for 

 0.1 N HC1 and 0.1 N H 2 SO4, since both are strong acids; or, in 

 other words, H 2 SO 4 combines in equivalent proportions with egg 

 albumin. The curve for H 3 PO 4 is the highest curve and if we 

 compare the values for H 3 PO 4 with those for HC1 (or H 2 SO 4 ) 

 we notice that for each pH the ordinate for H 3 P0 4 is as nearly 

 three times as high as that for HC1 as the accuracy of our experi- 

 ments permits. This means that phosphoric acid combines 

 with albumin (inside of the range of pH of our experiment) in 

 molecular proportions and that the anion of albumin phosphate 

 is the monovalent anion H 2 PO 4 . 



The values for oxalic acid are for pH below 3.2 almost but not 

 quite twice as high as those for HC1, indicating that for these 

 values of pH oxalic acid combines to a greater extent in molecular 

 and only to a small extent in equivalent proportions with 

 albumin. 



These combining ratios of the four acids named with crystalline 

 egg albumin are, therefore, the same as those which would be 

 found if we substituted the crystalloidal base NH 3 for the colloid 

 egg albumin, titrating in the same range of pH. 



From the curves just discussed, the amount of acid in combi- 

 nation with 1 gm. of originally isoelectric crystalline egg albumin 

 in a 1 per cent solution of this protein at different pH can easily 

 be calculated. Let us assume the acid added to isoelectric 

 albumin to be HC1. If, e.g., at pH 3.0, 6 c.c. of 0.1 N HC1 are 

 contained in 100 c.c. of the 1 per cent solution of the originally 

 isoelectric albumin (as indicated in Fig. 4), part of the acid is in 

 combination with the albumin and part is free. How much is 



