Specimens of the Silesian oxide of zinc, and of the precipitate, were afterwards sent to Strorneyer, who ascertained that the phenomena presented by this par ticular oxide, were owing to the presence of the pecu liar metal which he had discovered in the compound of zinc prepared at Salsgitter, and to which he had given the name of cadmium.
Cadmium is procured by dissolving the substances containing it in sulphuric acid, and passing a stream of sulphuretted hydrogen through the solution. The pre cipitate formed, after being well washed, must be dis solved in muriatic acid, and the excess of acid driven off by heat. What remains is dissolved in water, and carbonate of ammonia is added in excess, to dissolve the copper and zinc precipitated by the sulphuretted hydro gen. In this way carbonate of cadmium is obtained, the carbonic acid of which is expelled by heat. The oxide is then reduced by exposing it with charcoal to a high temperature. C_tchniutn is of a light whitish colour,, inclining to grey, very nearly resembling that of tie. It possesses considerable brilliancy, and takes on a fine polish. It is of a compact texture, and possesses also considerable lustre. It is likewise very ductile, and may be beat into thin plates.
The specific gravity of cadmium at 82 is 8.604. After being hammered, its specific gravity is increased to 8 694.
Cadmium, when subjected to caloric, fuses, and on cooling, it crystallises in octahxdrons. At a tempera ture not much exceeding that of the boiling point of mercury, it passes into vapour, which has no peculiar odour, and which condenses in small drops, exhibiting a crystalline structure.
By mere exposure to the air, cadmium does not undergo any change.
When heated in contact with atmospherical air, it takes fire. and forms a brownish yellow oxide.
Oxide of Cadmium. Cadmium has been made to unite with only one proportion'of oxygen.
The oxide has a yellowish green colour, which, how ever, by exposure to heat, becomes yellow. If the ap plication of the heat be long continued the oxide becomes brown. These changes in the colour are supposed to be owing to the difference in the cohesion of the body ; for when they are dissolved by an acid, the same com pounds are always formed.
The oxide of cadmium does not undergo any particu lar change by the application of heat to it. When kept at a white heat in a covered crucible for some time, it did not undergo fusion. When heated in contact with charcoal, it is reduced, the reduction taking place at about a red heat.
The oxide of cadmium is composed of 100 cadmium, 14.353 oxygen.
From this it is inferred that the equivalent number for the metal is 69.677, that of oxygen being I.
Phosphuret of Cadmium. Cadmium combines with phosphorus, and forms a grey-coloured compound, which is very brittle, and has a slight metallic lustre. When put on burning coals, it emits a beautiful flame, and is converted into phosphate of cadmium. Muriatic acid decomposes it with the evolution of phosphuretted hydrogen.
Sulphuret of Cadmium. Cadmium unites with sul phur; the sulphurct is however easiest formed by heat ing together the oxide and sulphur. It has a yellow colour when cold, but when exposed to heat it first be comes brown, and then crimson. At a white heat it fuses, and on cooling crystallizes in transparent yellow plates. Sulphuret of cadmium is decomposed by strong muriatic acid, with the disengagement of sulphurctted hydrogen. It is composed of 100 cadmium, 28.172 sulphur.
It is recommended as a good pigment.
Chloride of Cadmium is obtained in rectangular prisms, which, w hen subjected to heat, sublime, and effloresce on exposure to the ant. It is composed of 61.39 cadmium, 38.61 chlorine.
Iodide of Cadmium is obtained in hexacdral transpa rent colourless tables, which are decomposed at a strong heat, and part of the iodine escapes. is nut alteren on exposure to the air, and is not soluble in water. It is composed of 100 cadmium, 227.43 iodine.
The oxide of cadmium unites with acids, and forms with these, salts, which arc in general of a white colour. It is insoluble in the fixed alkalies. Ammonia, however, dissolves it. It is also soluble in carbonate of ammonia. Cadmium is acted on by nitric acid, nitric oxide being disengaged during the solution. It is also dissolved, though slowly, by sulphuric and muriatic acids, accom panied with the evolution of hydrogen.