W. O. Fenn 293 
extent of 2 per cent, and the writer has found that the same is 
true for a 1.87 per cent gelatin solution as the following figures 
indicate: 
Concentration of NaCl. Conductivity depressed. 
0.665 M. 1.51 per cent. 
Oreo: PALES OS 
O7145%: f° 66.50 G8 
0.0725 ;~ 12G5ltiy babs 
Similar measurements with CaCl, and NaSO, both on gelatin 
and on Witte’s peptone have shown that these salts combine 
more than NaCl. 
Pauli*4 has recently made a detailed study of the equilibrium 
between AgNO; and gelatin, ox serum proteins, and caseinogen 
by means of potentiometer and conductivity measurements. He 
finds that with increasing concentrations of AgNO; more and 
more combines with the protein until a maximum is reached. 
He believes that both ions combine equally. There is evidence 
that this is not true for the salts of the a’kaline earths. Pauli 
himself states”> that addition of Ba salts to proteins increases the 
H ion concentration of the solution as determined by indica- 
tors. If this were true it would indicate that the protein combines 
to a greater extent with Ba than with its anion. Fraenckel?® 
has also observed this fact for Ca salts by measurements with a 
concentration cell. Hardy,” furthermore, states that when CaCk 
precipitates globulin, free acid is formed in the solution as deter- 
mined by methyl orange. Billitzer?” has found cathodic convec- 
tion of proteins with the salts of alkaline earths, indicating the 
presence of a positive charge due to a greater combination of the 
protein with the cation than with the anion. As further evi- 
dence that salts with bivalent cations can deliver a positive 
charge to colloidal substances may be mentioned the work of 
Perrin?’ on endosmosis of various solutions through diaphragms 
of a great variety of substances and the similar work of Briggs,?° 
24 Pauli, Biochem. Z., 1917, Ixxx, 187. 
25 Pauli, Beitr. chem. Physiol. u. Path., 1904, v, 27. 
26 Fraenckel, P., Z. exp. Path. u. Therap., 1905, i, 439. 
*7 Billitzer, J., Z. physikal. Chem., 1905, li, 129. 
28 Perrin, J., J. chim. phys., 1904, ii, 601. 
* Briggs, T.R., J. Phys; Chem.:1917; xxi,s198: 
