542 Proteins 
in the hydrogen ion concentration is observed. In the M/8 NaCl 
solution where the membrane does not swell no change in the 
hydrogen ion concentration occurs. 
Dr. Dernby’s method was as follows. Pieces of pig’s bladder 
of equal weight (about 0.75 gm.) were put into 50 cc. of a salt 
solution for 1 hour, then washed repeatedly, and transferred into 
50 ce. of distilled water (except in the controls, where the bladder 
remained permanently in distilled water or in the salt solution). 
Table V gives his results. | 
TABLE V. 
Hydrogen ion concentration of a solution containing pig’s bladder treated 
as stated (expressed with Sérensen’s symbo! p 
After ete 
aisGliod-water.| "washed | Washedin | KCl | NEI | Na:SO. 
2 D & 
r. 
hrs. SS oe? 
0 About 6.4] 6.4 64 6.2 to 6.4 
4 ee Ade! 6.4 
1 6.4] 6.4 6.4 
Washed. 
2 yO. 64 724 6.8 6.8 6.9 
3 rea ven iels 7.2 710 7.0 7:0 
5 71 4-56.6 713 738 72 ee 
24 "ee. Go 7.4 3 7.3 7 
In these experiments the distilled water and salt solutions con- 
tained COz and this is the reason why at the first reading the H 
ion concentration is so high (6.2 to 6.4 instead of 7). The deter- 
minations prove that the solutions become more alkaline when 
the pig’s bladder was first treated with a neutral salt with mono- — 
valent cation. This agrees with our assumption of an elec- 
trolytic dissociation into a negative gelatin ion and a positive 
Nat ion, since slight hydrolytic dissociation would lead to the 
formation of a stronger base (NaOH) and a weaker acid, gela- 
tin-COOH. 3 | 
We had shown that the bivalent metals, Mg, Ca, Sr, and Ba, 
form in all probability less ionizable compounds with gelatin. — 
Hence we should expect that a previous treatment of pig’s blad- 
