Vol.. 6, 1920 
CHEMISTRY: E. J. COHN 
257 
gen ion concentration appear in the data. None the less, certain conclu- 
sions can quite safely be drawn, the more so since they are borne out by 
several other experiments. 
Table i 
Effect of NaCl upon Solubility and upon Acid Combining Capacity of Dialyzed 
TUBERIN 
NaCl ADDED TO 100 cc. OF DIALYSED POTATO PROTEIN. VOLUME INCREASED BY ADDED 
ELECTROLYTES TO 120 CC. 
S-a 0 
0 
0.25 
0.5 
1.0 
2.0 
5.0 
0 
0.25 
0.5 
1.0 
2.0 
5.0 
gm. 
gm. 
gm. 
g 
m. 
gm. 
mg. 
gm. 
g 
m. 
gm. 
gm. 
gm. 
gm. 
N/K 
100 
poti 
Tuberin dissolved (m 
g. nitrogen in 10 cc.) 
50 
1.58 
1.58 
1 
58 
1 
56 
1 
46 
5.96 
5 
79 
5 
79 
5 
79 
5.70 
3.40 
20 
2.67 
5.70 
5 
70 
5 
45 
5 
11 
4.34 
2.55 
5 
3.28 
3.33 
3 
37 
3 
50 
3 
49 
3 
45 
5.45 
5 
28 
5 
34 
4 
94 
4.09 
3.05 
3 
3.93 
3.97 
4 
02 
4 
09 
4 
03 
4 
13 
4.77 
5 
28 
4 
17 
4 
34 
4.68 
4.17 
2 
4.29 
4.34 
4 
41 
4 
44 
4 
34 
4.09 
4 
17 
4 
51 
4 
09 
4.26 
1 
5.22 
5.13 
5 
13 
3.40 
3 
83 
4 
09 
4 
43 
4.68 
4.60 
0 
5.71 
5.68 
5 
92 
5 
75 
5 
48 
5 
36 
2.47 
4 
09 
3 
66 
5 
02 
4.09 
4.26 
NaOH. 
0.5 
6.40 
6.23 
6 
02 
6 
28 
6 
10 
5 
84 
3.58 
4 
51 
4 
85 
5 
19 
4.77 
4.94 
1 
6.95 
6.76 
6 
78 
6 
52 
4.98 
4 
17 
4 
77 
5 
96 
5.19 
5.36 
3 
8.99 
8.77 
8 
71 
8 
77 
7 
95 
5.87 
5 
02 
5 
21 
5 
70 
5.87 
5.87 
5 
9.41 
9.06 
9 
23 
9 
25 
9 
09 
8 
98 
5.87 
5 
70 
5 
87 
5 
62 
5.87 
5.70 
10 
10.39 
10.09 
10.03 
10.20 
9 
72 
9 
83 
5.96 
6 
04 
5 
79 
5 
70 
5.87 
5.79 
I. the; ejffkct of sodium chloride upon the solubility of tuberin 
Solubility of Tuberin in Salt Solution. — The tuberin that had been pre- 
cipitated by dialysis, in the way that has been described, must not be re- 
garded as pure protein, but rather as a natural protein compound. It 
contained phosphorus and may have contained calcium. It was, however, 
largely redissolved by salt. 
The solubility of the tuberin was increased by the addition of sodium 
chloride to the systems that were otherwise unchanged. It was increased 
more by sodium chloride in the systems which contained small amounts 
of sodium hydroxide. However, when a small amount of acid was added 
the power of sodium chloride to increase the solubility was greatly weakened. 
This "effect of minute quantities of acid on the solubility of a globulin in 
salt solutions" appears to be quite general. It was studied by Osborne 
and Campbell in 1897^ and will be discussed later in this paper. 
In our experiments, which were extended over a wider range of hydrogen 
ion concentration, the effect of sodium chloride steadily decreased as the 
acidity increased, until at hydrogen ion concentrations in the neighborhood 
of 10 ~^ N, the solubility of the protein was nearly independent of the salt 
concentration. 
