420 
DR. JOHN STENHOUSE ON THE ACTION OF 
cent. From these determinations, therefore, there can be no doubt that the Populus- 
nigra also yields nitropopulic acid. I think there is good reason for expecting, there- 
fore, that the other species of Poplars will also yield nitropopulic acid, which I be- 
lieve will be found characteristic of the Poplar tribe. 
It has long been known, through the researches of Braconnot and other chemists, 
that the family of Poplars contains two crystallizable, very analogous principles, viz. 
salicine and populine. Now salicine, as was first observed by Piria, when it is distilled 
with a mixture of bichromate of potash and sulphuric acid, yields salicylous acid. 
On subjecting, therefore, separate quantities of the extracts of Populus balsamifaa 
and P. nigra to distillation with bichromate of potash and sulphuric acid, I succeeded 
in procuring a considerable amount of salicylous acid from both of them. There is 
every reason to believe, therefore, that both of these Poplars contain salicine, which 
is probably the source of much of the nitropicric acid which they yield when digested 
with nitric acid. The nitropopulic acid, which appears characteristic of the Poplar 
tribe, I strongly suspect will be found to result from the action of nitric acid upon 
the populine they contain ; though, for the present, I only throw out this idea as a 
probable conjecture. 
In order to be quite certain that the other nitrogenous organic acid obtained from 
both these Poplars, and accompanying the nitropopulic acid, was really the nitro- 
picric acid, as its external characters seemed to indicate, a quantity of its purified 
potash salt was subjected to analysis. 
0*555 grm. salt gave 0*182 sulphate of potash=0*0984 potash. 
0*4075 grm. salt gave 0*401 CO2 and 0*028 water. 
12 C 
Calculated numbers. 
900*00 26*94 
Found numbers. 
26*83 
2 H 
25*00 
0*75 
0*76 
3 N 
525*75 
15*74 
13 0 
1300*00 
38*94 
KO 
588*94 
17-63 
17-73 
3339*69 
100*00 
It is clear from these results that the acid in question is really the nitropicric, just 
as I had previously supposed. 
In conclusion, I subjoin a tabular view of the formulae of nitropopulic acid and its 
salts : — 
Nitropopulic, dried in vacuo 
Nitropopulic, dried in the aii 
Potash salt 
Soda salt 
Neutral baryta salt . . . 
Basic baryta salt . . . 
Silver salt 
HO, C,, H3 N2 0,3 
HO, Ci4 H3 N2 Oi3-f-2 Aq 
KO, C,4 H3 N2 0,3 
NaO, C.4 H3 N2 0,3 
BaO, C'h H 3 N2 0,3 
2BaO, C,4 H3 N2 0,3 
AgO, Ch H 3 N2 0,3 
