PAPAIN-PROTEOLYSIS. 167 



and likewise the control were continued for 75 hours. Diges- 

 tion was stopped by heating the mixture to boiling. It will 

 be noticed in these experiments that the proportion of papain 

 employed was quite small, considering the low digestive 

 power of the enzyme. 



The mixtures were analyzed as follows: The undissolved 

 residue, made up largely of an insoluble antialbumid-like sub- 

 stance, together with some unaltered proteid, was collected on 

 a weighed filter, washed thoroughly with water and lastly with 

 alcohol, then dried at 110 C. until of constant weight. The 

 filtrate and washings were then neutralized with dilute acid, 

 and the neutralization precipitate so obtained was collected on 

 a weighed filter, washed with water until free from salts, dried, 

 and weighed. To determine the albumoses, the neutral filtrate 

 and washings were concentrated to a small volume and then 

 precipitated while still hot by saturation with pure neutral 

 ammonium sulphate, giving heed to Kuhne's latest modifica- 

 tions of the method.* The precipitate was filtered by the aid 

 of a hot-water funnel and washed free from peptone with a hot 

 saturated solution of ammonium sulphate.f The precipitate, 

 together with the adherent ammonium sulphate, was then 

 washed into a weighed capsule with hot water, the mixture 

 evaporated to dryness, and finally dried in an air-bath at 110 

 C. until of constant weight. Obviously, the weight so obtained 

 was the combined weight of the albumoses and ammonium sul- 

 phate. To ascertain the value of the latter, the mixture was 

 treated with water containing a little hydrochloric acid, the 

 fluid made up to a definite volume, and in an aliquot portion of 

 the latter the sulphuric acid was determined in the usual 

 manner by precipitation with barium chloride. From the 

 weight of barium sulphate thus obtained the amount of am- 

 monium sulphate was calculated and deducted from the com- 

 bined weight of the albumoses and ammonium salt. The 

 amount of true peptone formed was obtained in this experi- 

 ment by deducting the combined weight of the antialbumid 



* Loc. cit. 



t Continued until the filtrate failed to show any biuret reaction. 



