250 REPORT OF THE CHEMIST OF THE 
(1) Increase of temperature increases the rate at which equi- 
librium is approached. Thus, 25° and 45° C. curves rise more 
rapidly than those for 0° C. 
(2) Increase of temperature increases the final amount of hydro- 
chloric acid that disappears as free acid, when there is marked solu- 
tion of casein due to the higher temperature, as shown by curves 
for 45° C. in Figs. 9-12 and for both 25° and 45° C. in Fig. a2: 
The soluble acid-casein apparently contains a larger proportion of 
hydrochloric acid than the undissolved casein, which would have 
the effect of raising the curve when the soluble form occurs. Our 
observation has been that solution of casein, whether resulting from 
increase of temperature, concentration of acid or length of contact 
with acid, is accompanied by fixation of more acid than is taken up 
when no solution occurs. 
(3) When rise in temperature does not result in solution of pro- 
teid, it apparently decreases the amount of acid fixed. This may 
be seen by comparing the value expressed in Fig. 8 (A and B), 
which indicates a value of 97 to 100 for the ratio of acid in casein 
to acid in water at equilibrium at 25° C., with the results in Table 
VIII, which indicate a value of 147 for the ratio at 0° C. The 
same conclusion is shown by comparing the 25° and 0° C. curves of 
Figs. 9, 10 and 11, which express results obtained with acids suff- 
ciently dillute to avoid very marked solution of proteid even at 25° 
C. The 25° curves rise more rapidly at first than do those for 0°, 
because the higher temperature increases the rate at which they 
approach equilibrium. They soon approach a horizontal position, 
however, and after 214 to 4 hours cross the 0° curves, evidently 
inclining toward lower equilibrium values. With N-125 acid, how- 
ever, the concentration is sufficient to dissolve decided amounts of 
proteid within a few hours at 25° C. Consequently, we should 
expect the 25° curve as well as that for 45° in Fig. 12 to be 
abnormally high, which is the case. 
It was our purpose to study the effect of temperature upon equi- 
librium under conditions such that solution of proteid would be 
more completely avoided than at the temperatures used in the ex- 
periments given above, using only the most dilute solutions, and — 
hastening equilibrium by constant agitation in order to produce 
more uniform conditions, which would show in more regular curves. 
