ION SERIES AND THE PHYSICAL PROPERTIES OF 

 PROTEINS. II. 



By JACQUES LOEB. 

 {From the Laboratories of The Rockefeller Institute for Medical Research^ 



(Received for publication, September 8, 1920.) 



/. Combining Ratios of Acids and Bases with Gelatin and the Swelling of 



Gelatin. 



In this paper we will continue the demonstration of the relation 

 between the combining ratios of acids and bases with proteins and the 

 effect of ions on the physical properties of proteins. This demonstra- 

 tion com.pletes the proof that the purely chemical forces of primary 

 valency determine the reactions of proteins with other compounds. 



It is generally stated in colloidal literature that gelatin swells more 

 in chlorides, bromides, or nitrates than in water and that it swells less 

 in citrates, acetates, tartrates, phosphates, and sulfates than in water. 

 The author of this statement is Hofmeister^ who was a pioneer in 

 this work and who cannot be blamed for not having considered cer- 

 tain sources of error in his methods. In Hofmeister's experiments 

 gelatin blocks were put into salt solutions of so high a concentration 

 that — as we now know — no specific ion effects could be expected and 

 the slight differences in swelling actually observed by him were proba- 

 bly merely accidental. He even mentions that sugar solutions have 

 a "dehydrating" effect, and this fact alone should have warned chem- 

 ists against using his experiments for conclusions concerning the spe- 

 cific effects of ions on the physical properties of colloids. As far as 

 the writer can determine from the literature the discrimination 

 between "hydrating" and "dehydrating" ions originated from these 

 experiments. 



^ Hofmeister, F., Arch. exp. Path. u. Pharmakol., 1891, xxviii, 210. 



247 



