27S 
ON POPULUS TREMULOIDES. 
greasy stain on paper; and when mixed with a solution of 
carbonate of potassa formed a soapy compound. 
Experiment 4. — Lime, Potassa, and Iron. 
An ounce of the bark was incinerated and treated by boil- 
ing water until all the soluble matter was removed, and the 
solution filtered; to this liquid a solution of chloride of pla- 
tinum, with a few drops of hydrochloric acid, was added and 
boiled to dryness; on mixing a few drops of w T ater, it 
yielded crystals of a yellow color, of the double chloride of 
platinum and potassium: also, upon evaporation of another 
portion of the solution, it yielded crystals of carbonate of po- 
tassse, (by the absorption of carbonic acid from the atmos- 
phere during evaporation;) the residuum, after treating the 
ashes by boiling water, was acted upon by nitric acid, and 
the nitric solution diluted with water. To this was added 
oxalate of ammonia in solution, when it yielded a copious 
precipitate, having all the characteristics of oxalate of lime. 
To another portion of the nitric solution ferrocyanuret of 
potassium was added, and the well known precipitate of Prus- 
sian blue was produced. 
Experiment 5. — Gallic Jlcid+ 
A strong decoction of the bark was made, and after filtering 
and digesting with hydrate of alumina, it yielded no precipi- 
tate with a solution of gelatin: but with a solution of persul- 
phate of iron it formed a dirty brown precipitate, indicating 
the existence of gallic acid. 
Various processes were tried to obtain the bitter principle 
of this bark; for instance, precipitating the decoction by sub- 
acetate of lead ; removing the lead by hydrosulphuric acid; 
concentrating the liquor to the state of an extract; redissolv- 
ing in alcohol boiling with animal charcoal, filtering and eva- 
poration; precipitating with acetate of lead; and boiling with 
chalk to precipitate the lead, evaporation, &c. These and 
