Jaeques Loeb 541 
RCOOH + NaCl —- RCOO-Na + HCI. 
In this case the supernatant solution should have an acid reac- 
tion. This was not the case. 
Pauli makes another suggestion based on the fact that proteins 
in general are stronger acids than bases, and that hence they must 
undergo a stronger hydrolytic dissociation where they act as 
base than where they act as acid. If such a protein combines 
with NaCl the Cl would undergo hydrolytic dissociation and be 
washed away as free HCl. But if this were the case, the water 
with which NaCl-gelatin is washed should have an acid reac- 
tion. Although we were not able to demonstrate,such an acid 
formation, we should remember that little acid was formed at 
the utmost and that some of it may have been bound again by 
gelatin molecules. The important fact is that under the influ- 
ence of a neutral salt, of the type NaCl, the gelatin forms a sodium 
gelatinate, which dissociates electrolytically into a negatively 
charged gelatin ion and a positively charged metal ion—that of 
the salt used. ) 
This assumption is further supported by hydrogen ion deter- 
minations which Dr. Dernby has made in my laboratory and 
which I incorporate here with his permission. The writer had 
shown in a previous paper that pig’s bladder behaves like pow- 
dered gelatin inasmuch as it shows a considerable additional 
swelling in H,O when previously treated with NaCl or any neu- 
tral salt with univalent cation; while no such additional swelling 
in H-.O occurs after previous treatment with neutral salts with 
bivalent cation. Dr. Dernby found that when the membranes 
treated with m/8 NaCl (or KCl, ete.) were afterward put into 
distilled water the latter became slightly alkaline; but that this 
was not the case when the pig’s bladder was previously treated 
with CaCle. 
Dr. Dernby determined the hydrogen ion concentration by 
Sérensen’s colorimetric method, using his standard phosphate 
solutions and neutral red as indicators. In all these experiments 
the hydrogen ion concentration changes in the same way as the 
swelling. Where a strong additional swelling occurs, as in H,O 
after a previous treatment in NaCl, the hydrogen ion concen- 
tration diminishes; where no additional swelling occurs no change 
