142 ^■Iccount of a new Vegetable Suhsfance. 



If this precipitate be exposed to a white heat it becomes of 

 a blackish gray, scarcely inclining to green, and weighing 

 only 1"285. On continuing the fire, the mass approaches 

 the metallic state more and more, and becomes niajrnetic. 

 This is eflccrcd mvich more speedily if the oxide be moist- 

 enfcd with a little oil. 



If caustic aniinnnia be added in excess to a nitric solution 

 of nickel, a precipitate is formed, resemblins; in colour am- 

 nioniurc of copper, bi.it mA so deep. This colour sometimes 

 changes in a couple of hours to an amethvst-red, and to a 

 violet, which colours arc converted into an apple-green on 

 tlie addition of an acid, and again to a blue and violet on 

 the addition of anmionia. If, however, we add to the solution 

 of nickel a solution of copper, so as to produce no perceptible 

 change, the colour of the precipitate formed by ammonia 

 ceases to assunie a red tinge, and the red colour of the 

 ammoniureof nickel disappears on the addition of a little 

 ammoniure of copper; whence it follows, that every pre- 

 cipitate of nickel by ammonia which retains its blue colour, 

 has copper cond^ined with it. 



XXX. Account of a new Fegetahle Substance discovered 

 by M. RosK*. 



zxFTER standing some hours, a decoction of the root of 

 elecampane {inula helenium) deposits a white powder, ap 

 pearing very much like starch, but difliering from it both in its 

 principles and in its manncrof action with other substances. 

 l.'l his substance is insoluble, generally, in cold water: -- 

 When triturated with it a white milky liquor is formed, 

 which soon deposits a heavy white powder, and leaves the 

 supernatant water clear and colourless. 



2. In boiling water it dissolves very well. On boiling 

 one part of the white powder witii four parts of water, a 

 complete solution is obtained which passes tlirough filter- 

 ing paper while hot, but, on cooling, acquires a mucila- 

 ginous consistence and a dull colour. In the course of 

 some hours this solution deposits the greater part of the 

 dissolved substance in the form of a compact white powder. 



One part of gum-arabic, dissolved in four parts of water, 

 IS much thiekiT, of a more tenacious consistence, and froths 

 lightly, which tlie solution of the powder from the elecam- 

 pane root does not. 



3. The solution of the white powder mixed with an equal 

 quantity of alcohol is at first clear, but. in a little time the 

 powder separates in the form of a tumid white sediment, 

 leaving the fluid above it t-i'ansparent. A solution of gum - 



• From GMi-ns Joirna!, vol. iii. 



■i " arable 



