g20 MR CONN ELL ON SULPHURET OF CADMIUM. 



above-mentioned change of colour by heat described by Berzelius as a character 

 of the artificial sulphuret of cadmium. It was next found that the precipitates 

 caused by potash and by carbonate of ammonia were not dissolved by excess of 

 the precipitants. These reactions all tended to confirm the above idea of the na- 

 ture of the contained metal ; but what left the matter no longer doubtful, when 

 taken in conjunction with the above-mentioned characters, was observing that a 

 mm-iatic solution with excess of acid, gave a fine yellow precipitate, with a cur- 

 rent of sulphuretted hydrogen, exactly similar to that obtained by the same 

 means from a similar solution of metallic cadmium. When a precipitate was no 

 longer caused by the current of sulphiu-etted hydrogen, and the solution of the 

 mineral was then neutrahzed by ammonia, a few dark flocks fell of sulphuret of 

 iron. Through the neutralized liquid a fresh current of sulphuretted hydrogen 

 was passed, but no farther precipitation ensued, shewing the absence of zinc, a 

 conclusion farther confirmed by finding that the excess of potash and of carbo- 

 nate of ammonia, used as precipitants, took up nothing. 



The muriatic solution of the mineral gave a yellow precipitate with hydro- 

 sulphuret of ammonia, and white precipitates with prussiate of potash, oxalate 

 of ammonia, and phosphate of soda; and no precipitate with sulphuric acid. 

 A piece of zinc threw down reduced metal as a grey ramification. 



These various reactions left no doubt that the mineral under examination 

 was sulphuret of cadmium ; that it contained no sensible admixture of zinc ; and 

 that the only impurity which could be detected was a slight trace of iron. The 

 different observations were farther confirmed by comparative trials made on a 

 solution of metallic cadmium. It Avas therefore quite evident that the mineral 

 was not only a new one, but one of much interest, since, so far as I know, no 

 separate ore of cadmium had ever before been discovered ; that metal having hi- 

 therto been found merely as a constituent, or more probably as an admixture, in 

 certain ores of zinc, to the extent of a few per cents. 



The materials sent to me by Professor Jameson gave no farther means of 

 prosecuting the examination of the mineral, either chemically or in relation to 

 specific gravity ; but by the kindness of Lord Greenock, I was furnished for 

 these purposes with the largest, although not the most perfectly formed, crystal 

 which I have yet had an opportunity of seeing. His Lordship has also lately ob- 

 tained one very finely crystalhzed specimen, although not of a large size, which 

 is evidently a six-sided pyramid, -without any transverse streaking of the faces, 

 and terminating in a short six-sided prism ; but as the crystalline form of the 

 mineral is under investigation by Professor Jameson, and there are some mo- 

 difications which will require a careful examination, I wish to say nothing far- 

 ther on the subject of its crystallization, except as respects the particular crystal 

 analyzed. 



