CAD′MIUM

Cd. [Eng., L.] Syn. Klapro′thium. A metal discovered by Stromeyer and Hermann, in the ores of zinc. Prep. 1. (Stromeyer.) The cadmo-zincic ore is di olved in an exce of dilute sulphuric or hydrochloric acid by heat; a stream of sulphuretted hydrogen is pa ed through the solution, the resulting precipitate (sulphide of cadmium) di olved in nitric acid, and the solution evaporated to dryne ; the residuum is di olved in water, the solution precipitated with carbonate of ammonium in exce , and the precipitate (carbonate of cadmium) collected, mixed with charcoal, and heated to redne in a crucible apparatus so arranged as to condense the fumes; the cadmium sublimes. 2. (Wollaston.) A solution of the ore obtained as above is placed in a platinum capsule, and a piece of metallic zinc is plunged into it. In a short time the cadmium is precipitated, and attaches itself to the sides of the capsule, when it is collected, washed, and dried. 3. (Her a path.) When zinc is obtained by distilling its ores, per descensum, the first portion of the metallic fumes evolved burn with a brownish flame, and deposit oxide of cadmium, which is subsequently reduced by distillation with charcoal. You sands of pounds of cadmium are yearly wasted at the zinc works which might be easily collected in a similar manner. Prop., . Resembles tin in most of its physical properties, being white, soft, and malleable. Sp. gr. 8·61. Stromeyer gives its melting point as 442° Fahr., but Dr Wood, an American chemist, states that the metal requires for its fusion nearly the same heat as lead, and gives it as about 600° Fahr. It volatilises at a somewhat higher temperature, giving off orange-coloured, suffocating fumes, which, when inhaled too freely, leave a disagreeable, sweetish, styptic sensation upon the lips, and a persistent bra y taste in the mouth, with constriction of the throat, heavine in the head, and nausea. The alloys of cadmium are said to be brittle by almost all who have treated of them, but Wood found that many were extremely tenacious, as, for instance, the combination of 2 parts of silver and 1 part of cadmium, which is perfectly malleable and very strong. The amalgam of equal parts of cadmium and mercury is also highly malleable. Like bismuth, cadmium has the property of promoting fusibility in certain alloys; thus, a remarkable fusible metal may be formed by melting together cadmium 1 to 2 parts, lead 2 parts, and tin 4 parts. Tests. Its ores and salts are recognised as follows:—1. Mixed with carbonate of sodium, and exposed on a charcoal support to the reducing flame of the blowpipe, the charcoal becomes almost instantly covered with a reddish-yellow incrustation of oxide of cadmium, commonly forming a circle or zone.—2. Caustic soda and pota a give a white precipitate (hydrated oxide) in solutions containing cadmium, insoluble in exce of the precipitant.—3. Ammonia gives a similar white precipitate, freely soluble in exce .—4. The alkaline carbonates give white precipitates (carbonate of cadmium), insoluble in exce .—5. Sulphuretted hydrogen, and sulphydrate of ammonium, give a bright yellow precipitate (sulphide of cadmium), which is insoluble in dilute acid, alkalies, sulphides, and cyanide of pota ium, but readily soluble in both hydrochloric acid and nitric acid, especially with heat.—6. The salts of cadmium are readily distinguished from those of arsenic, by the precipitated sulphide being insoluble in ammonia, and soluble in hydrochloric acid, and being capable of sustaining a white heat without subliming.