New York AGRICULTURAL EXPERIMENT STATION. 255 
aliquot portions of the filtrate titrated as in the preceding ex- 
periments. The results are given in the following table: 
TABLE IJI.—AmountT oF Hyprocutoric AcID NEUTRALIZED BY ONE GRAM OF 
BASE-FREF C4SEIN, AMOUNTS AND DILUTION oF ACID VARYING. 

Amount of acid Acid equal to Acid equal to 
eee ct poe ie + used equal to n-100 HCl in n-100 HCl in 
3 i n-100 HCl. filtrate. proteid. 
ces ce. ce, 
50 n- 200 25 18.4 6.6 
40 n- 100 40 33.6 6.4 
30 n- 80 SER, 30.0 7.5 
20 n- 60 gona 25.6 sf 
The results in Table III indicate that when we treat the 
base-free casein wth a more concentrated acid solution, we have 
more acid left in the proteid. This is as we should expect under 
the conditions of experiment. The acid that is not recovered in 
the filtrate must either combine with the proteid or adhere to it 
mechanically. We made no attempt te wash the adherent or oc- 
cluded acid free from the proteid, since any thorough washing 
would remove some of the combined acid. Therefore, the more 
concentrated the acid used in treating the proteid, the more acid, 
as measured by titration, adhered to the proteid in addition to 
the fixed amount of acid that combined with the proteid, as com- 
pared with treatment with an equal volume of more dilute acid. 
It is not easily conceivable that such an amount of acid as is 
represented by about 6 cubic centimeters of ai 
acid should be held only mechanically by one gram of casein, 
hydrochloric 

when we used solutions so dilute as those with which we worked. 
Bearing on this point the following additional experiments were 
made: 
(1) We suspended a weighed amount of base-free casein in 50 
cc. of water, let stand 15 minutes, added —— hydrochloric acid at 
the rate of 6 ce. for one gram of casein and made the volume to 
100 ce. with water. After filtration, the filtrate was titrated and 
the result showed that 5.2 ce. of —~ hydrochloric acid had been 
held by one gram of casein. 
(2) The experiment was repeated, allowing the mixture to 
stand one hour after addition of acid. The result was the same 
as before. 
