272 Dr. Clarke on Cadmium. [Apuil, 



Article V. 



Observations upon the Ores tvhich contain Cadmium, and upon 

 the Discovery of this Metal in the Derbyshire Silicates and 

 other Ores of Zinc. By Edward Daniel Clarke, L.L.D. 

 Professor of Mineralogy in the University of Cambridge, 

 Member of the Royal Academy of Sciences at Berlin, &c.&c. 

 In a Letter to the Editor of the Annals of Philosophy. 



(To Dr. Thomson.) 



DRAR SIR, Cambridge, Feb. 18, 1820. 



In vol. xiv. of your Annals, p. 269, you gave some new details 

 respecting Cadmium from the " Annalen der Physik," by M. 

 Stromeijer, which excited in my mind a very great desire to see 

 the ores which are said to contam this curious metal. Some 

 varieties of radiated blende from Przibram, in Bohemia, are 

 described as containing two or three per cent, of cadmium. At i 

 a sale which took place soon afterwards in London, I procured 

 specimens of the particular mineral thus alluded to, which were 

 isold under the name of splendent fbrous blende from Przibram, 

 pronounced Pritzbram. 1 found afterwards that they had been 

 brought to England by Mr. J. Sowerby, of Lisle-street, a dealer 

 in minerals, from whom I afterwards obtained more of the same 

 substance. L^pon my return to Cambridge, I endeavoured to 

 obtain Cadmium from this ore, and succeeded, not following 

 exactly the process mentioned by M. Stromeyer, because I made 

 use of muriatic acid, in the first place, as a solvent, instead of the 

 sulphuric, as being easier of evaporation ; and hoping, by a 

 careful evaporation to dryness, to separate any lead that might 

 be present, the crystals of muriate of lead not being soluble in 

 distilled water. Before any thing further is stated, it may be 

 proper to describe the ore itself. The splendent fbrous blende of 

 Przibram, in its external appearance, is not unlike red hydrosul- 

 phtiret of antimony, but it is so highly splendent as to exhibit a 

 lustre nearly metallic, especially alter a fresh fracture. It exhi- 

 bits shining fibres, as radii diverging from a common centre, 

 imbedded in common massive blende, which also has somethings 

 of a radiated structure, and is associated with an aggregation of 

 cubic crystals of sulphurct of lead. The purer fibrous part of the 

 mineral, divested of the massive blende and of the sulphuret oflead, 

 was selected for experiment. Its specific gravity in distilled 

 water, at a temperature equal to 55° of Fahrenheit, is exactly 

 4000. The Abbe Haiiy makes that of sulphuret of zinc, or 

 the commen blende, to be equal to 4,1665. 



(A.) Twenty-five grains of this mineral triturated in a porcelain 

 mortar exhaled a strong smell of sulphuretted hydrogen simply 



