286 Effects of Electrolytes on Gelatin. I 
ture, and the abscisse the concentration of salt in the gelatin 
before titration with alcohol. 
In general, all the curves show that with increasing concentra- 
TABLE III. 
Effect of Various Salts on the Precipitation of Gelatin by Alcohol. 
MeCh. CaCle ' MnCl Mg(NOs)2 SrCh 
Concen- | Alcohol Concen-|Alcohol | Concen- | Alcohol | Concen- | Alcohol | Concen- | Alcohol 
tration of} to pre- | tration | to pre- |tration of} to pre- |tration of} to pre- |tration of] to pre- 
MgCl. |cipitate.jofCaCh.|cipitate.| MnCle. | cipitate. | MgNOs. | cipitate.| SrCle. | cipitate. 
M ce. M CC. M cc. M cc. M cc. 
0.5 11.1 | 2t8b5e di 285020 11725.0"150 13.05 | 1.63 | 10.9 
0.25 10.95) 1.42 | 11.65) 0.25 | 10.75 | 0.5 1159 0.82 | 11.25 
0.125" | 10.35) 0.71 | 11.5 |.0.125 } 10:2 | 0.25 |.10.65 |) SO Seis 
0.0625] 9.9 | 0.35 | 11.4 | 0.0625) 9.75 | 0.125 | 9.65] 0.2 | 11.2 
9.2} 0.18 | 11.1 | 0°0312) 9.0 | 0.0625) 8.4 0.1 | 10.4 
0.0156} 7.8 | 0.09 | 10.1 | 0.0156) 7.5 | 0.0312) 7.385 } 0:05 1) 9r25 
4.2 | 0.0 
NHaCl NHsSCN MgSO. ZnSOa* 
Concen- Aleohol Concen- | Alcohol Concen- Alcohol Concen- Alcohol 
tration of to pre- | tration of | to pre- tration of | to pre- tration of to pre- 
NHC. cipitate. | NH4SCN.| cipitate. MgSOu. cipitate. ZNSOs;. cipitate. 
M Ce. M RB M ce. M (pe 
2.87 1230952520 13.35 0.5 4.4 0.125 2.0 
1.43 11.5 1.0 135 0.25 4.75 0.0625 3.0 
0.72 10.15 | 0.5 9.75 0.125 9.05 0.0312 3.05 
0.3 85150] O8Z5 8.4 0.0625 | 5.25 0.0156 3.1 
0.18 pels: OFl25 TALS 0.0312 5.05 0.0078 3.4 
0.09 6.65 | 0.0625 | 6.35 0.0156 | 5.15 0.0039 3.85 
0.0 4.4 0.0078 | 4.9 0.00195 | 4.0 
0.0 4.5 0.0 4.0 
*2 per cent gelatin A, over night at 30°C. Not strictly comparable 
to the other experiments in this table. 
For all except ZnSO, (as noted) gelatin B was used (3 per cent) and 
the tubes stood over night at 26°C. before titrating. For further details 
see Table II. 
tions of the salts, more and more alcohol is needed to precipitate 
until a maximum is reached. Fig. 2 shows that as the valence 
of the cation increases, the salt concentration at which the maxi- 
mum is reached decreases. Valence, however, is not the only 
