Alloys of Cadmium

Lithium. - Cadmium forms with lithium the two compounds LiCd and LiCd₂.

Sodium dissolves cadmium slowly. NaCd₂ occurs in octahedral crystals of D₄²⁰ 5.669 that are slowly acted upon by water and melt at 395° C. It is brittle, harder than cadmium, unaffected by absolute alcohol, and coloured like its components.

The cubical crystals of NaCd₆ melt at 363.5° C. There may be compounds with a higher percentage of cadmium, and NaCd₅ is said to exist.

Potassium, according to the freezing-point curve, forms the two compounds KCd₇ and KCd₁₁.

Aluminium. - Cadmium and aluminium are not miscible in the fused state. When the two metals are melted together and allowed to remain molten, the cadmium, containing a few tenths per cent, of aluminium, sinks, and the aluminium, containing 2.3 per cent, of cadmium, floats.

Thallium. - Cadmium is slightly soluble in thallium in the solid state.

Tin and cadmium are reciprocally soluble to the extent of about 3 per cent, in the solid state; the molten metals mix in all proportions. CdSn₄ is said to exist, though Mazzotto thought that the metals probably formed no compounds.

Lead and cadmium are miscible in all proportions.

Bismuth and cadmium, when molten, are miscible in all proportions, but they apparently do not mix in the crystalline condition.

Alloys of cadmium and nickel cannot be prepared with more than 15 per cent, of nickel because of the volatility of the cadmium; they are not magnetic. Cd₄Ni exists.

Cadmium and antimony mix in all proportions. The compound Cd₃Sb₂, crystallising in the rhombic system, separates under appropriate conditions from the molten mixture of the two metals. It is less stable than CdSb, and tends to decompose into the latter. Cadmium-antimony alloys of approximately atomic composition have high thermo-electric power.

If D is the density of the amalgam at 25° C., and p the gram of cadmium per 100 grm. of mercury,

D = 13.5340-0.0606p.

The temperature coefficient is -(0.0024+0.0003p). An amalgam saturated with cadmium at 25° C. contains 5.574 parts of that metal in every 100 parts of mercury.

Cadmium dissolves in mercury to a considerable extent and diffuses readily through it. The amalgams can be prepared by adding cadmium to mercury and warming; they are also readily obtained by electrolysing cadmium salts with a mercury cathode.

According to Smith, cadmium does not form definite compounds with mercury, though some cadmium mercurides have been reported. Cadmium amalgams with over 18 per cent, of cadmium are solid.

Alloys of cadmium with up to 10 per cent, of calcium are stable in air and are little acted on by water. The action of water is more vigorous with greater proportions of calcium. The compounds CaCd and CaCd₃ appear to exist, and possibly Ca₂Cd₃.

A black spongy alloy containing equal quantities of gold and cadmium is precipitated by metallic cadmium from a solution of a gold salt. The hardness of gold-cadmium alloys attains a maximum when either 18.30 or 51.63 per cent, of cadmium is present. There is also a maximum brittleness at the latter percentage.

According to Saldeau, gold and cadmium form the two compounds AuCd and AuCd₃. Vogel detected these two compounds and also Au₄Cd₃. Hey cock and Neville said they obtained AuCd.

Silver and cadmium alloy in all proportions. Any addition of silver to cadmium raises the freezing-point. High proportions of cadmium make the alloys brittle. An alloy has been obtained by the action of cadmium on a solution of silver sulphate.

The compounds AgCd, AgCd₃, AgCd₄, Ag₂Cd, Ag₂Cd₃, Ag₃Cd₂, and Ag₄Cd have been said to exist.

Copper and cadmium alloy in all proportions. The alloys remain silvery white up to 60 atoms per cent, of copper, and pass from yellow to red as the atomic proportions increase from 68 to 90. Much cadmium makes them soft; with increasing proportions of copper they become harder and more brittle. Copper-cadmium alloys have been obtained by treating solutions of copper salts with metallic cadmium.

The compounds Cu₂Cd and Cu₂Cd₃ have been obtained, and CuCd₃ is said to exist. The heat of formation of Cu₂Cd₃ has been determined as 48 Cal., and its heat of fusion as 26.05 Cal. per grm.