SALTS OF ALBUMIN AND ACIDS 



67 



again. As we can now see, this is due to the appearance of free 

 Cr ions in high concentrations of albumin, which take part in 

 the lowering of the freezing point. With lower albumin content 

 the excess of acid present represses the ionisation of the albumin 

 chloride. The actual results are shown in Table 25, in which A 

 is the observed depression, D the depression calculated from 



the sum of acid and albumin molecules, and the differ- 

 ence produced per gram of albumin. 



Table 25. 



(g = grams egg albumin ; 0-05 N HCl in all cases.) 



We can now summarise the information supplied by these 

 various researches on the behaviour of albumin and glutin in 

 the presence of hydrochloric acid as follows. On adding acid 

 to a given weight of protein, combination occurs to an extent 

 which increases with increase of acid up to a maximum. Thus, 

 for i gm. serum albumin the maximum combination is with 

 1-66 x io- 3 gm. mol. HCl or 60-59 m g- HCl. ; for i gm. glutin 

 the value is 1-5 x io- 8 gm. mol. HCl or 54 mg. HCl. When 

 combination occurs, the hydrogen of the acid forms w r ith the 

 albumin an electro-positive albumin ion, while the chlorine ions 

 largely remain unattached. With excess of acid, the ionisation 

 of the protein chloride is suppressed, as is shown by a rapid 

 increase in the combination of the chlorine ions with the pro- 

 tein, and also by a decrease in the quantity of albumin trans- 

 ported in the electric field. The hydration of the protein 

 particles, moreover, increases as the combination with acid 



52 



