4 



" The first plant experimented on with this view, was the Populus 

 halsamifera, as representing the numerous family of the Poplars. A 

 quantity of the smaller branches of this tree, cut into pieces, was 

 exhausted with boiling water. The dark-coloured bitter-tasted liquid 

 which it yielded was evaporated to the state of an extract, which 

 was digested for nearly twenty- four hours Vv'ith dilute nitric acid. 

 This strongly acid solution was evaporated to dryness on the water 

 bath, the dried residue was dissolved in a considerable quantity of 

 hot water, and the solution after cooling was carefully filtered. The 

 clear liquid, after concentration to a very moderate bulk, was exactly 

 saturated with carbonate of potash. A yellow crystalline sediment 

 quickly appeared. It consisted of nitropicrate of potash, and the 

 potash salt of a new acid, to which the author has given the name of 

 nitropopulic acid. The mixed potash salts were then collected ou a 

 filter, dried by pressure, and were treated with a cold solution of 

 dilute carbonate of potash, which readily dissolved out the nitro- 

 populate of potash, while it left the nitropicrate of that base unacted 

 on. The two salts were then separated by filtration, the nitropi- 

 crate remaining on the filter, while the nitropopulate was dissolved 

 in the alkaline liquid. The solution was next slightly supersaturated 

 with hydrochloric acid, v.'hen the nitropopulate of potash precipi- 

 tated as a compact crystalline powder, which was purified by re- 

 peated crystallizations out of hot water. When pure, the potash 

 salt, which crystallizes in small lemon-yellow prisms, is boiled with 

 a considerable excess of hydrochloric acid, and, on the cooling of 

 the solution, the nitropopulic acid is deposited in silky needles, 

 forming concentric groups of a pale yellow colour. By digestion 

 with animal charcoal, the nitropopulic acid is rendered perfectly 

 colourless. It is very soluble in water, and still more so in weak 

 and strong spirits of wine, ^y digestion with strong nitric acid, 

 it is rapidly converted into nitropicric acid. In several of its cha- 

 racters nitropopulic acid bears a considerable resemblance to indi- 

 gotic acid. When subjected to analysis, the formula of nitropopulic 

 acid dried in the air, was found to be Cj4 H3 No 0,3 + HO + 2Aqu ; 

 that of the acid dried at 212° F., H3 0^3 + HO. 



The potash, silver, soda and baryta salts were also analysed. 



The Populus nigra, when treated with nitric acid, was also found 

 to yield nitropopulic acid, which appears therefore to be character- 

 istic of the poplar tribe. 



An extract was also prepared from Salix russelliana, or the Bed- 

 ford-willow, which, when it was digested with dilute nitric acid, 

 yielded a great deal of oxalic and nitropicric, but no nitropopulic 

 acid. Extracts of the Cytisus laburnum, or the laburnum-tree ; of 

 the Sweteyiia wahogani, or the mahogany-tree; of the Pyrus mains, 

 or the apple-tree of the Cratcegus oxyacantha, or the hawthorn ; 

 of the Ribes nigrum, or the black currant bush ; of the Betula alnus, 

 or the alder ; of the Vlex europceus, or the furze ; of the Calluna 

 vulgaris, or common heather ; of the root of the Curcuma longa, or 

 turmeric ; of the seeds of the JBixa orellana, or annotto ; of the 

 Sambucus nigra, or the elder ; of the Cytisus scoparius, the Spar- 



