Jacques Loeb 535 
ing and reaching its maximum at M/1024. Gelatin treated with 
M/8 NaCl and then treated with solutions of non-electrolytes 
from 2 m down swells to the same extent as if it were treated 
with distilled water. This harmonizes with the assumption that 
the swelling is determined by the degree of electrolytic dissocia- 
tion of the gelatin. 
3. It has been shown by Pauli and his fellow workers that 
ionized protein can no longer be precipitated by alcohol.* If the 
additional swelling of gelatin in distilled water caused by the 
previous treatment with m/8 NaCl was due to an increase in ioni- 
zation such gelatin should resist precipitation by alcohol. This is 
most strikingly the case. When we dissolve the three kinds of 
TABLE I. 
Increase in swelling of powdered gelatin (which had first been perfused 
with 50 ec. m/8 NaCl) after three perfusions with 25 ce. of 
=H 
ate etrow eS Weals obeelterielic 
es falas |e fe |e al | ele 
Nao lect 4 0 0 2.51 6 |15)21 |33.5/42 
Glycerol....... 34 (1387 |40/40 |40 |43 |42 |42 |40 |41/41 [41 [43/42 
Cane sugar..... 35 141/49 |49 {51 {51 {50 {50 [51/51 [51 48 
Ethyl alcohol. .|42 5/48. 5/54/48 .5|48 .5|48 5/49 .5/49 .5)49.5)47/47.5|47 50.5 
powdered gelatin, I treated with water alone, II treated first 
with M/8 NaCl and then with water, and III treated with salt 
(m/8 NaCl) alone, and measure the quantity of alcohol needed 
to precipitate 5 cc. of a 3 per cent gelatin solution of each of the 
three samples, we shall find that it requires about 5 cc. of 95 
per cent alcohol to cause a heavy precipitate in I, and about 7 
ec. to cause the same precipitate in III; while in II no precipitate 
is formed even by the addition of 20 cc. or more of alcohol; the 
solution assumes only a bluish tint upon the addition of about 
20 ec. of alcohol. | 
4. It was shown in the previous paper that any neutral salt 
with univalent cation acts like NaCl upon powdered gelatin, 
inasmuch as a perfusion of gelatin with a neutral salt of Li, K, 
or NHy, when followed by a perfusion with distilled water, 
causes an additional excessive swelling; while the perfusion of the 
powdered gelatin with neutral salts of the bivalent cations, Mg, 
Ca, Sr, and Ba, d6es not cause any additional swelling when the 
THE JOURNAL OF BIOLOGICAL CHEMISTRY, VOL. XXXIII, NO. 3 
