ON POPULUS TREMULOIDES. 
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black precipitate of iodide of starch; and when a solution of 
subacetate of lead was added, a white, insoluble compound of 
gum and protoxide of lead immediately subsided; also, with 
a solution of the persulphate of iron it yielded a precipitate 
of a bluish black color; and to confirm the nature of this solu- 
tion a solution of gelatin was added, which precipitated 
tanno-gelatin. With a fresh portion of the infusion, the tinc- 
ture of muriate of iron formed a black precipitate of the tan- 
nate of iron ; with the ferrocyanuret of potassium the infusion 
afforded no precipitate. 
Experiment 2. — Extractive Matter and Chlorophylls. 
A portion of the fresh bark was bruised, and a pint of alco- 
hol, of 36°, was poured over it in a displacement filter; after 
being returned and repassed during three hours it was of a 
greenish color, and very bitter. It was then evaporated to 
dryness, and consisted of chlorophylle and extractive matter, 
associated with the bitter principle, as well as a portion of 
tannin ; by the action of heat, chlorophylle was changed to 
black from green: and, when treated with cold water, the 
extractive matter and tannin were dissolved, and the chloro- 
phylle rose to the surface. The liquid, when filtered, was of 
a dark brown color; when tested by reagents, the following 
were the results: with persulphate of iron a blackish precipi- 
tate; with lime water a slight precipitate of a dark red 
color; and with a solution of gelatin a precipitate of a brown 
colour. 
Experiment 3. — Fixed Oil. 
To a fresh portion of the bark four ounces of sulphuric 
ether were added in a displacement filter, and returned several 
times during two hours; the etherial tincture had a bright 
green color, and very bitter taste; and upon evaporation it 
yielded a yellow oil, with the chlorophylle in small propor- 
tion, of a black color, floating on the surface. This oil left a 
