274 Dr. Clarke on Cadmium. [April, 



flame, became, either a dark slag, or an orangc-coIonred oxide, 

 \intil the whole was dissipated by increasing the temper- 

 ature. The last globules of the dark slao- among the oraiwe- 



• 111 • ® 



coloured oxide had a metallic appearance. When borax was 

 added to the above, a fine amethyst Culour appeared, while 

 hot, which vanished when it became cold. To prove that 

 this precipitate by zinc was really cadmium, I redissolved it 

 in muriatic arid, and, after the usual process, sulphuretted 

 hydrogen gave its beautiful orauge-coloured precipitate, and 

 hydrate of potass a while precipitate, as before; which became 

 ledissolved by adding liquid ammonia. 



I have been the more particular in detailing these experiments, 

 because upon their accuracy mainly depends the validity of my 

 subseqiient remarks respecting the presence of Cadmium in other 

 ores oi' zinc. In the course of them, I had made some observa- 

 tions which led me to conclude that Cadmium is more remarkably 

 characterized by a tendency to crystallization, than even aitti- 

 moni/, or any other metallic body. When the muriate of cad- 

 mium' is dissolved in a very considerable body of water, far 

 below saturation, as it adheres to the sides of a glass vessel and 

 becomes drv, it shoots out into transparent fibrous crystals, which 

 radiate in a very beautiful manner. Many otiier solutions of the 

 metal are moreover characterized by a tendency to crystalliza- 

 tion. Having observed this, 1 began to suspect that a radiated 

 structure in ores of 2/«c might, perhaps, be an indication of the 

 presence of Cadmium in these ores ; and accordingly I began the 

 examination of a specimen of silicate of zinc, which I had 

 brought from the same sale, and which had been described in the 

 yale catalogue as electric calamine from Freiiherg. It exhibited 

 black diverging fibres, accompaaiied by an orange-coloured (;arth, 

 nnd, perhaps, it maybe the sort oi black fibrous blende in which 

 Stroimiicr is said first to have discovered Cadmium. 



Having dissolved a part of this mineral in sulphuric acid, and 

 evaporated the acid almost to dryness, a sufficient quantity of 

 distilled water was added to enable the fluid to pass the filters 

 without destroying them ; and having collected the clear hquor, 

 sulphuric acid was again added, that an excess of the acid might 

 be present according to tStromeijei's process. A stream oC sul- 

 phuretted luidronen nas was then sent through the solution, and 

 immediately a most vivid orange-coloured precipitate began to 

 fail. With this precipitate I. repeated the experiments before- 

 mentioned, of solution in muriatic acid, Jk.c. ik.c. and after the 

 usual process obtained carbonate of cadmium, as before, having 

 all the characters of that carbonate. 



I made several attempts to revive the metal, but witli little 

 success. By heating the carbonate and expelling the acid, I 

 obtained the oxide of cadmium, and by placing this in a glass 

 tube containing hydrogen gas, and making the tube red-hot, a 

 brilliant white-lookms: metallic appearance became fixed upon 



