PHYSIOLOGICAL CHEMISTRY. 



show in this way. On the other hand in the course of the 

 week's digestion there is a decrease in the " free " hydrochloric 

 acid as measured by aid of the dimethylaminoazobenzene indi- 

 cator. The titration here is not as sharp as with phenol- 

 phthalein, but close enough to indicate the facts. An amount 

 of acid corresponding to 9 cc. of the N/io alkali was " free " 

 immediately after mixing. About 5 cc. had evidently com- 

 bined with the egg albumin to form the acid albumin. As 

 digestion progressed and smaller molecules were formed more 

 acid was required to unite with these. Finally the perfectly 

 uncombined acid amounted to the equivalent of 6.5 cc. of 

 alkali only. Before the end of the digestion bodies were 

 formed which probably acted as both acids and bases with the 

 proper indicators. The amino acids are of this character. 



Results of somewhat similar nature have often been re- 

 ported. The short table below contains figures given by Chit- 

 tenden. A mixture was made containing pure egg albumin, 

 water, pepsin and enough 0.2 per cent hydrochloric acid to 

 produce a neutral result with the Gunzburg reagent. 24 cc. 

 of the acid was used for this. The mixture was placed in 

 the thermostat and kept warm (38) for some days. From 

 time to time a test was made for free acid and if none was 

 found more was added to reach the neutral point with the 

 reagent. In this way a considerable additional amount of 

 acid was consumed. The table gives the results, which show 

 a very marked increase in the amount of acid combined. 



Time. 



2h. 45111. 



5h. 3om. 

 2ih. ism. 

 26h. 3om. 

 2gh. 3om. 

 45h. 



OQh. 



94h. 



Acid Added to Show Trace of Free Acid. 



4.5 cc. 0.2 per cent HC1 



i.o 



3-0 



i.o 



1-5 

 i.o 

 o.o 



3.0 



2.0 



17.0 



The irregularities in the figures are doubtless due to the lack 

 of delicacy in the indicator used. 



