164 On two Metals, found in the black Ponder 



iuto its composition. The inethod which I used for dis- 

 solving it, was similar to that employed uy M. ^''auquelin ; 

 the aheniate action of caustic alkali, and of an acid. 1 put 

 a (uiantitv of the powder into a crucible of silver, with a large 

 proportion of pure drv soda, and kept it in a red Jieat for 

 sonic time. The alkali being then dissolved in water, had 

 acquired a dcej) orange, or brownish-\cllow 'colour, but 

 much of the powder remained undissolved. This powder, 

 digested in marine .acid, gave a dark blue solution, which 

 afterwards became of a dusky olive-green, and finallv, by 

 continuing the heat, of a deep red colour. Part of the pow- 

 der, being yet undicsolved by the marine acid, was heated as 

 before with alkali ; and, by the alternate action of the alkali 

 and acid, the whole appeared capable of solution. At each 

 operation some silex was taken up bv the alkali j and, as this 

 continued till the metaliic part was entirely dissolvctl, it 

 seems to have been chemicallv combined with it. 



The alkaline solution contains the oxide of a volatile 

 metal, not yet noticed, but which I shall presently describe, 

 and also a small proportion of the other metal. If this solu- 

 tion is kept lor some weeks, the latter metal separates spon- 

 taneously from it, in the form of very thin flakes, of a dark 

 colour. 



The acid solution also contains both the metals, but prin- 

 cipally that which has been mentioned by the French che- 

 mists. The properties of this last metal, which they have 

 remarked, arc those of giving a red colour to the triple salt 

 of plaiina '.\ ith sal-ammoniac, of not being altered by muriate 

 of tin, and of giving, with pure alkali, a dark brown precipi- 

 tate. M. Vauquelin also adds, that it is precipitated by 

 galls, and by prussialc of potash ; but I should rather ascribe 

 these precipitates to some impurity, and probably to Iron. 



As it is necessarv to give some name to bodies which have 

 not been known before, and most convenient to indicate 

 by It some characteristic property, I should incline to call 

 this metal mdium, from the striking variety of colours which 

 it gives, while dissolving in marine acid. 



In order to obtain the comj)ound of this metal with ma- 

 rine acid in a pure state, I tried to niake it crystalline. 



By slow evaporation of the solution, only an imperfectly 

 -crvstallized mass was produced; but this, being dried on 

 blotting-paper, and dissolved In water, afforded, by again 

 evaporating as before, disthict octaedral crystals. These 

 crystals, dissolved in water, gave a deep red coloured solu- 

 tion. Inclining to orange. With an infusion of grills, no 

 jprccipitate \\as formed, but the colour was instantly, and 



almost 



