R. H. Chittenden — Ferments of Pineapple Juice. 305 



acetic acid. The dialysis was continued for a week or more longer, 

 until every trace of sulphate was removed, when the reaction of the 

 solution was found distinctly alkaline, so much so that no precipi- 

 tate separated even on boiling the solution, although it became quite 

 opaque at about 78° C, until a drop of acetic acid was added. In 

 another preparation, where the alkalinity was less pronounced, the 

 solution after dialysis of all, or nearly all of the salt, gave a floccu- 

 lent precipitate at 85° C. 



The faintly alkaline solution of the proteid yielded a precipitate 

 on addition of 0*2 per cent, hydrochloric acid, very soluble in a 

 little salt solution and in a slight excess of 0-2 j^er cent. acid. Only 

 a portion of the substance was separated however, by this method 

 of precipitation. The filtrate, which appeared nearly neutral to 

 test papers, on being heated grew turbid at 7.3° C, without however 

 any separation of flocks until the solution was boiled. The slight floc- 

 culent precipitate which then resulted was wholly soluble in 0-5 per 

 cent, sodium carbonate, and nearly so in 0-2 per cent, hydrochloric acid. 

 P^irther, the filtrate had marked proteolytic power and treated with 

 nitric acid gave a distinct turbidity, not appreciably diminished by 

 warming the mixture. That portion of the proteid precipitated by the 

 dilute hydrochloric acid gave, after solution in dilute sodium^ chlo- 

 ride, essentially the same reactions as the fox*egoing, so that evidently 

 the two fractions were identical. 



This preparation of the ferment agreed fairly well in its reactions 

 with the substance separated by sodium chloride. Like the latter, 

 the turbid solution resulting from the dialysis cleared up on addition 

 of a little salt solution, likewise on the addition of a few drops of 

 dilute nitric acid, while more acid produced a second turbidity not 

 readily dissolved by an excess of the acid, or by heat. With the 

 biuret test, a more distinctly reddish color was produced than here- 

 tofore seen. 



There are, therefore, two good methods for the isolation of the 

 proteolytic ferment from pineapple juice ; one by saturation of the 

 neutralized fluid with sodium chloride, the other by saturation with 

 magnesium sulphate. In our opinion, the former method yields a 

 product with the strongest proteolytic power, although this needs to 

 be verified by further observations. As to the exact chemical nature 

 of the ferment, or of the body it is associated with, we are not yet able 

 to speak with perfect confidence. It is our opinion that the proteo- 

 lytic body separated by the above methods is a mixture of a globulin 

 and a proteose, but as yet we have not been able to accomplish a dis- 



