240 REPORT OF THE CHEMIST OF THE 
TABLE I[X.— SHOWING RELATION oF AMOUNTS OF HyprocHLoric AcIp FIXED 
BY CASEIN TO CONCENTRATION OF AcID, 25°C. 
_——— 
















Proportion in saree aha ei Percentage Ratio of D 
and : Sone ere of acid in | conc’n acid ere 
ec Duration of acid in of acid in cit : ; f 
approximate f : original in casein luti 
normality oO water casein aathiindg to solution 
Atiacid contact. |(=ce. N-1000 (=ce. N-1000 taken un 4 cone amend of 
eee acid in Icc. jacid in 1 gm. Ie pacnia nina t ae casein. 
2 solution). casein). y : ; 
Series 1 0 4085 0 0 OQ}! * || Sa aee 
N-2000 30 min. .4597 Soe 7.8 69.9 0 
828 cc. for hte 4550 36.0 8.7 T9341 0 
1 gram of 2 hrs. .4507 39.7 9.6 87.8 0 
casein 4 hrs. .4476 42.1 Oe 94.1 0 
Series 2 0 .4985 0 0 QO." Syl eee 
N-2000 ih) lake: 4156 Sou 16.6 79.8 0 
400 ce. 24 hrs. .4064 36.8 18.5 90.6 0 
for 1 gram pemorss .4050 37.4 18.8 92.4 0 
of casein acSs 4011 39.0 19.5 97.1 0 
Series 3 0 .9970 0 Of 9 0 a ae eee 
N-1000 15 min. .5556 44.1 44.3 79.4 0 
100 cc.- 50 min. 15300 46.4 46.5 87.0 0 
for 1 gram 14 hrs. .5181 47.9 48.0 92.4 0 
of casein 3 brs. . 5066 49.0 49.2 96.8 0 

The results embodied in the preceding table are also shown in 
Fig. 8 in the form of curves A and B. It is noticeable that the. 
initial rate at which acid is taken from N-1000 solution is greater 
than from N-2000, as would be expected, but the two curves ap- 
proach nearly the asymptote. The points (XX and °) for the two 
N-2000 solutions lie on the same curve A. 
Extraction of hydrochloric acid taken up by casein.— The re- 
action by which casein fixes acid is reversible. By treating with 
pure water casein that has taken up acid, part of the acid passes 
from the casein back into the surrounding water. | 
The method of performing the experiment was as follows: In 
weighed Jena flasks were placed 1-gram portions of casein and 100 
cc. portions of N-500 HCl. The mixtures were shaken continuously 
for 30 minutes, in order to allow the casein to take up acid under 
conditions not permitting appreciable amounts of casein to go into 
solution. The mixtures were then allowed to settle for about 5 
minutes and the supernatant liquid decanted as completely as possi- 
ble through weighed Gooch crucibles, into which the decantation 
usually carried 10 to 20 milligrams of casein. The filtrate (1) 
was kept for examination. The crucibles were dried and weighed 
in order to find out how much casein had escaped from the flask 
