298 Dr. Clarke on the [Oct. 



which I left in a porcelain vessel for several hours. Afterwards 

 collecting the clear infusion which had assumed a deep red 

 colour, I submitted it once more in a Florence flask to the heat 

 of an Argand lamp, and evaporated the whole to dryness. 

 There remained, at the bottom of the flask, a black carbonaceous 

 substance which had the smell of burned sv.gar. A portion of 

 this substance being placed within a cavity scooped in a stick of 

 charcoal, was exposed to the action of the common blow-pipe ; 

 and, as it fused veiy readily, it was soon reduced to a very small 

 black bead ; which, resisting the utmost action of the blow-pipe, 

 was held for a considerable time in a state of fusion, attended 

 with phosphorescence and ebullition. After being cooled, its 

 form was perfectly globular, and it was attracted and taken up 

 by a magnet. It was then hard enough to be driven into the 

 end of a deal splinter, and filed. Particles with metallic lustre 

 were by this means rendered conspicuous. I have sent one of 

 these beads to you for examination, corresponding in appearance 

 with the iron I before transmitted to you, and having the same 

 magnetic character. But in other trials, made with the same 

 carbonaceous substance, sometimes I obtained the black magnetic 

 beads, and at other times, owing to causes I am unable to 

 explain, it burned to a white ash, containing no magnetic particles. 

 The same substance being exposed to the action of the gas 

 blow-pipe, exhibited combustion with minute sparks, and was 

 speedily converted into a white opaque glass ; probably owing to 

 a portion of lime which has been detected in the precipitate 

 thrown down by ammonia from the infusion of roses, as described 

 in my last letter ; and which acting as a solvent for the colouring 

 matter,* may, perhaps, explain the presence of a metallic oxide 

 in the vegetable. 



(B.) — The magnetic beads, mentioned in A, being dissolved in 

 acids, and the acid, in every instance, evaporated to dryness, 

 and distilled water added, and afterwards filtered, tincture of 

 galls threw down a dark precipitate ; and prussiated alkali, a 

 deep emerald green precipitate ; the latter, collected on a filter, 

 became afterwards blue. 



(C.) — The precipitates mentioned in B exposed to the action 

 of the common blow-pipe upon charcoal, were again converted into 

 beads acting upon the magnet; and after admitting the action of 

 the file again, disclosing a metallic lustre. Exposed to the gas 

 blow-pipe, combustion with scintillation ensued, as in the com- 

 bustion of particles of iron. 



(D.) — The presence of iron appearing to have been thus satis- 

 factorily ascertained in the carbonaceous substance obtained by 

 the evaporation to dryness of an infusion of roses, as related in 

 A, some of this substance was triturated in a porcelain mortar, 

 and being reduced to a fine powder, was boiled in diluted 



* See Chaptal, vol. iii. p. 154. 



