52 Trimble. — Mangrove Tannin. 



The other more important constituents were determined to 

 be, mucilage 1.72 per cent., glucose 0.81 per cent., albumen- 

 oids 7.02 per cent., starch 4.27 per cent., and cellulose 27.49 

 per cent. Tannin was determined by gelatin and alum, and 

 found to be, in the air-dry bark, 23.92 per cent. ; this was an 

 average of three closely agreeing results. For future com- 

 parison it may be well to note that this by calculation indi- 

 cates 27.19 per cent, of tannin in the absolutely dry bark. 



Preparation and Purification. 

 A quantity of the tannin was prepared by extracting the 

 finely powdered bark with commercial ether (specific gravity 

 0.750). After recovering most of the solvent, the remaining 

 extract was distilled to dryness under reduced pressure. The 

 residue was dissolved in ether of the same specific gravity, 

 and the solution concentrated to dryness under reduced 

 pressue, which had the effect to render the tannin quite por- 

 ous and in a condition to be dissolved by water, which was 

 next used. The filtered aqueous solution was carefully treated 

 with solution of neutral lead acetate. In this operation it is 

 to be noted that the first few drops of the reagent caused a 

 precipitate, which on stirring disappeared. A further addi- 

 tion of the reagent caused a precipitate of the coloring 

 matter, and on filtering a yellow filtrate was obtained. 

 This filtrate was agitated successively with three portions of 

 acetic ether, which removed the tannin. The precipitate was 

 suspended in water and decomposed with hydrogen sulphide, 

 the mixture filtered and the filtrate, after heating under re- 

 duced pressure to remove hydrogen sulphide, was treated 

 with lead acetate as before and the filtrate agitated with 

 acetic ether, which removed an additional quantity of tannin. 

 This acetic ether solution was mixed with that from the pre- 

 vious agitation and the whole distilled to dryness, the residue 

 dissolved in ether with some water, and again distilled to dry- 

 ness under reduced pressure. 



Properties. 



The tannin obtained by the above process was in light red- 

 dish-yellow porous masses, completely and readily soluble in 



