Rubidium amalgam

Alloys are metallic substances containing two or more elements which are miscible when molten and do not separate when solidified. They may be liquid or solid. This mixture of elements, usually but not necessarily metals, allows careful manipulation of strength, melting point, corrosion resistance, magnetic, thermal, electrical, and other properties steel, for example, is an alloy of iron and carbon often present with nickel, chromium, copper, aluminium, boron, tungsten, manganese, cobalt, silicon, and other elements. 

Alkali metal alloys and alkaline earth metal alloys have a wide range of applications. The degree to which the alloys retain the pyrophoric or water-reactive properties of their parent metals depends on their concentration in the alloy, the modifying nature of the alloyed components, and the state of subdivision. Many commercial alloys of this type, present no hazard. Others, such as the potassium-sodium alloys used in heat exchangers, present significant concern. Other alkali and alkaline earth metal alloys include 

Amalgams are alloys of mercury with other metals used extensively as chemical reagents and catalysts. The proportion of mercury dictates whether the amalgam is solid or liquid. They include sodium amalgam (Na Rgy), used to manufacture sodium hydroxide, and dental amalgams (alloys of mercury with some combination of silver, copper, tin, gold, or silver) used to fill dental cavities. 

Alkali metal, see Terminology, Metals, p.242 Alkaline earth metal, see Terminology, Metals, p.242 

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Rubidium can be liquid at room temperature. It is a soft, silvery-white metallic element of the alkali group and is the second most electropositive and alkaline element. It ignites spontaneously in air and reacts violently in water, setting fire to the liberated hydrogen. As with other alkali metals, it forms amalgams with mercury and it alloys with gold, cesium, sodium, and potassium. It colors a flame yellowish violet. Rubidium metal can be prepared by reducing rubidium chloride with calcium, and by a number of other methods. It must be kept under a dry mineral oil or in a vacuum or inert atmosphere. 

Mercury forms amalgams with numerous metals. Usually, this conversion is very exothermic, therefore it can present risks the reaction can become violent if a metai is added too quickly into mercury. Accidents have been described with caicium (at 390°C), aluminium, alkali metals (lithium, sodium, potassium, rubidium) and cerium. Some of these alloys are very inflammable, in particular the Hg-Zn amalgam. 

Rubidium alloys easily with potassium, sodium, silver, and gold, and forms amalgams with mercury. Rubidium and potassium arc completely miscible 111 the solid state. Cesium and rubidium form an uninterrupted series of solid solutions. These alloys, in various combinations, are used mainly as getters for removing the last traces of air in htgh-vacmim devices and systems. 

I Attention is called to the close analogy in modes of preparation and properties of the caesium and rubidium compounds. For caesium-amalgam, see this series, VoL III. 

Schlenk and Marcus in 1914 found that triphenylmethyl chloride reacted with sodium amalgam in dry ether solution, when the operation was carried out in an atmosphere of nitrogen. The resulting compound, sodium triphenylmethyl, was a brick-red mass, decomposed by moisture or carbon dioxide. Kraus and Kawamura in 1928 showed that triphenylmethyl chloride reacts with sodium and potassium in liquid ammonia, but that the potassium compound is more stable than the sodium derivative. A number of compounds similar in structure to triphenylmethyl have since been sho wn to give similar reactions. Rubidium and esesium also form similar derivatives. ... 

MERCURIO (Italian, Spanish) (7439-97-6) Violent reaction with alkali metals, aluminum, acetylenic compounds, azides, boron phosphodiiodide (vapor explodes), bromine, 3-bromopropyne, chlorine, chlorine dioxide, ethylene oxide, lithium, metals, methyl silane (when shaken in air), nitromethane, peroxyformic acid, potassium, propargyl bromide, rubidium, sodium, sodium carbide. Forms sensitive explosive products with acetylene, ammonia (anhydrous), chlorine, picric acid. Increases the explosive sensitivity of methyl azide. Mixtures with hot sulfuric acid can be explosive. Incompatible with calcium, sodium acetylide, nitric acid. Reacts with copper, silver, and many other metals (except iron), forming amalgams. 

Incompatibilities and Reactivities Acetylene, ammonia, chlorine dioxide, azides, calcium (amalgam formation), sodium carbide, lithium, rubidium, copper ... 

The direct metallothermic reduction of pollucite ore with sodium metal is the primary commercial source of cesium metal. In the process, raw pollucite ore is reduced with sodium molten metal at ca. 650"C to form a sodium-cesium alloy containing some rubidium as impurity. Fractional distillation of this alloy in a distillation column at ca. 700"C produces 99.9 wt.% pure cesium metal. Cesium can also be obtained pyrometallurgiccdly reducing the chloride CsCl with calcium metal or the hydroxide CsOH with magnesium metal. Nevertheless, the electrolytic recovery of a cesium amalgam from an aqueous solution of cesium chloride can be achieved in a process similar to the chlor-alkali production with a mercury cathode. Afterwards, the cesium is removed from the amalgam by vacuum distillation. However, cesium metal is produced in rather limited amounts because of its relatively high cost (US 40,800 /kg)... 

Also see Barium, Cadmium, Magnesium, Potassium, Rubidium, and Strontium amalgams... 

Amalgams Cesium Lithium Potassium Sodium Rubidium Also see Silver-silver chloride Also see Silver-silver chloride Also see Silver-silver chloride Also see Silver-silver chloride Also see Silvei silver chloride Also see Silver-silver chloride... 

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