American Senna. 
tween the two kinds of senna, I performed the followS^x^OFW 
periments : 
1. To a filtered decoction of the leaves, a solution of ace- 
tate of lead was added, so long as a precipitate fell ; this was 
separated by filtration : the excess of acetate of lead, by hy- "'' ; 
dro-sulphuric acid; sulphuret of lead by another filtration: , ', . 
this solution was evaporated to dryness, and treated with 
pure alcohol, the alcoholic solution evaporated, and then 
treated with sulphuric acid, to decompose the acetate of 
potassa which it contains : the sulphate of potassa is sepa- 
rated by filtration : the excess of sulphuric acid by acetate of 
lead : the excess of acetate of lead by hydrosulphuric acid : 
sulphuret of l'ead by filtration; the alcoholic solution now 
evaporated, yielded the active matter of the plant. 
2. Macerated the leaves for several hours in cold water ; 
the liquid was separated by means of a sieve, and filtered. 
On being heated to ebullition it becomes turbid : another por- 
tion yielded a grayish precipitate, with a solution of corro- 
sive sublimate. 
3. The leaves were digested in alcohol until every thing 
soluble was taken up, expressed and dried ; they were then 
treated with cold water. The solution thus obtained, gave a 
flocculent precipitate with acetate of lead ; and a brownish 
precipitate with permuriate of iron. On concentrating a por- 
tion of the solution, it yielded a precipitate on the addition of 
alcohol. 
4. The residue of the leaves from last experiment, were 
treated with boiling water ; this solution yielded a blue pre- 
cipitate with tincture of iodine ; subacetate of lead threw 
down a whitish precipitate. 
5. Macerated the leaves in cold water until every thing 
soluble in that menstruum was taken up ; expressed and dried 
them. They were now treated with alcohol ; the alcoholic 
solution filtered and evaporated; the substance left was 
treated with boiling water, which took up a small quantity 
of soluble matter. The residue was of a deep green colour, 
soluble in alcohol and ether, slightly soluble in boiling water; 
insoluble in cold water. 
