NITRIC ACID ON VARIOUS VEGETABLES. 
421 
The following are the formulae of a few of the other nitrogenated acids which most 
closely resemble nitropopulic acid : — 
Indigotic acid HO, H4 N O9 
Nitropopulic acid HO, C14 H, Ng 0,3 
Nitrophenesic acid .... HO, C,2 H3 Ng 0,3 
Nitropicric acid HO, C,2 H2 N3 0,3 
Oxypicric acid HO, C12 H2 N3 Ojj 
It is plain, therefore, that nitropopulic acid only differs from nitrophenesic acid by 
two equivalents of carbon. 
Salix Rtisselliana, or Bedford Willow. 
An extract was prepared from the wood and branches of the Salix Russelliana, 
exactly in the way already described in the two preceding instances. When digested 
with dilute nitric acid, it yielded a great deal of oxalic and nitropicric, but no nitro- 
populic acid. The following pretty numerous list of trees and shrubs, when treated 
with nitric acid, also yielded oxalic and nitropicric acids : — 
1 . Cytisus laburnum, or the Laburnum-tree. 
2. Swietenia mahogani, or Mahogany Wood. 
3. Pyrus malus, or the Apple-tree. 
4. Crataegus oxyacantha, or the Hawthorn. 
5. Rihes nigrum, or the Black Currant-bush. 
6. Betula alnus, or the Alder. 
7. Ulex europceus, or the Furze. 
8. Calluna vulgaris, or Common Heather, 
9. The root of the Curcuma longa, or Turmeric. 
10. Extract of seeds of the Bixa orellana, or Annotto. 
11. Samhucus nigra, or Common Elder. 
12. Cytisus scoparius, the Spartium scoparium of Linn., oj* Common Broom. 
The extracts of Quercus rohur, or Common Oak, and of Betula alba, the Beech-tree, 
when digested with nitric acid, only yielded oxalic acid, but no nitropicric or any 
analogous nitrogenated acid. It is somewhat remarkable, therefore, that of the ex- 
tracts of seventeen vegetable substances no fewer than fifteen should, when treated 
with nitric acid, yield nitropicric acid ; while two of their number, in addition to 
nitropicric, should also yield nitropopulic acid, and only two out of the seventeen 
should produce oxalic acid, unaccompanied by a nitrogenous organic acid. 
The results of these experiments seem to indicate therefore that a far greater num- 
ber of plants are capable of yielding nitropicric acid than has generally been sup- 
posed, those which fail to do so apparently constituting a very small minority. I 
fully expected to have met with a greater variety of nitrogenated acids, and am rather 
surprised that I did not find either the indigotic or oxypicric acids, 
MDCccLi. 3 I 
