1820.] extracted from Pyrites at Fahlun. 2S 



more notable quantity ; and we must hope that it will one day 

 be in our power to recognize and collect it. 



M. Gahn had shown me some years ago a small piece of a 

 mineral which he had received under the name of Swedis/i ore of 

 tellurium. I made some fruitless attempts to extract telluriimi 

 from it, and at the time that I thought myself entitled to say that 

 it contained none of that metal, M. Gahn made me perceive the 

 strong odour of horseradish which it exhaled when heated before 

 the blow-pipe. The small quantity which we possessed being 

 consumed m our attempts to obtain tellurium, 1 was obliged to 

 defer the examination of it till 1 could procure a greater quantity 

 of it. 



During my experiments on selenium, I recollected this pre- 

 tended ore of tellurium, and having applied to the person who 

 had sent the specimen to Gahn, I was fortunate enough to obtain 

 a quantity sufficient for an analysis of it. 



As far as I can judge from the specimens of this mineral 

 which I have seen, it possesses the following properties : 



Its colour is leaden grey ; it has the metallic lustre ; the frac- 

 ture is granular and subcrystalline, without its being possible to 

 discover other signs of crystallization. It is soft, and may be cut 

 ■with a knife ; where cut, it has the brilliancy of silver. It 

 receives impressions from the hammer. 



• Before the blow-pipe, it melts, and gives out a strong smell of 

 horseradish, leaving a small grey metallic button, which conti- 

 nues long to exhale the smell. If we fuse it v/ith borax, that 

 saline substance becomes copper-green, and a brittle metaUic 

 button separates, which is a seleniuret of silver. A solution of 

 this mineral in boiling nitric acid mixed with cold water gives a 

 white precipitate, which is seleniate of silver, and which has 

 probably led to the notion that it was an ore of tellurium. 



The mineral is mixed with carbonate of lime and with black 

 parts, which, when scratched by the knife, assume the metallic 

 lustre, melt with difficulty before the blow-pipe, giving out the 

 odour of selenium, dissolve, when fused with borax, giving it the 

 green colour of copper, and exhibit no traces of reduced silver." 

 The black parts appear to be a serpentine imbibed with seleniuret 

 of copper. 



For analysis I selected pieces as pure as possible, and 

 I divided them into very small grains, to be sure tliat they con- 

 tained no visible portion of these foreign bodies. 



a. One hundred parts of the mineral were dissolved in boihng 

 nitric acid. The solution was diluted with boiling water, and 

 then tiltered. The liquid which passed fell into a solution of 

 muriate of soda, and the matter which remained upon the filter 

 was washed with dilute boiling nitric acid as long as the liquid 

 that passed through continued to trouble the solution of the 

 muriate. 



In this last solution, muriate of silver had precipitated, which. 



