282 REPORT OF THE CHEMIST OF THE 
NaHCoO,, is formed, this acid salt has apparently the same con- 
ductive as the neutral salt. Apparently the (H casein),®? (H, 
casein)™? . . . .. ions have the same conductivity as the (casein)” 
ion (n= valence of casein anion), the gain or loss of a hydrogen 
atom not appreciably affecting the velocity of the excessively large 
and complex casein anion. 
Laqueur (Beitr. Chem. Physiol. uu. Pathol., 7:273. 1905) mentions the 
fact that increase in the proportion of casein in a solution of sodium 
caseinate neutral to phenolphthalein does not appear to change the con- 
ductivity, and discusses the explanation mentioned above, also as less prob- 
able the one that the excess casein simply dissolves as free casein in the 
sodium caseinate solution. 
The constancy of the conductivity of solutions acid to phenolphthalein 
is shown more accurately by the figures of Long (Jour. Amer. Chem. Soc., 
28:377. 1906), although he does not call attention to this feature. Re- 
arranging Long’s results, so as to make this point clear, we have the fol- 
lowing table: 
N 
c. c.—Na OH. Reaction 
, 10 Grams Conductivity to of 
in 100 c. c. casein. «108 phenolphthalein 
1525 1234 { alkaline 
D2 SOD Giaie Parti eT ee Eee a ae D5 1006 Bie 
5.0 1012 acid 
(0.625 700 alkaline 
1 Es eS i et pons UA Tee Be Fe | Ye25 561 neutral 
2.50 563 acid 
(0.3125 380 { alkaline 
BOLO) arty ee eT ay ie Mens 5 nee bres 310 Estas 
a: 308 acid 
0.1562 | 209 alkaline 
RSL 2 i Sec cheered Soa eee 7 Ono kop 172 neutral 
(0.6250 { 168 acid 
BE AOGs ca rse i ncs ea Ae {0.1562 {93 { neutral 
LO Lal2o (93 acid 
The last two figures of each trio in the conductivity column agree closely. 
From the above discussion it is apparent that if casein acts as 
an acid with a definite neutral point correctly indicated by phenolph- 
thalein, as was apparently considered to be approximately the case 
by Laqueur and Sackur,' who based equivalent and molecular 
weight determinations upon this assumption, we should expect a 
neutralization conductivity curve descending in a straight line to 
the neutral point, and there breaking and becoming horizontal. 
* Beitr, Chem. Physiol. u. Pathol., 32193. 1903. 
