CHEMISTRY : Metal Cation Identification

Information on BARIUM

1. General Information


2. Occurence Uses and Properties


3. History of the Metal


4. Compounds
5. Back to Main Metal List

The earliest known alkaline earth was lime (Latin: calx), which is now known to be calcium oxide; it was used in ancient times in the composition of mortar. Magnesia, (the name derives probably from the ancient district of Magnesia in Asia Minor), the oxide of magnesium, was shown to be an alkaline earth different from lime by the Scottish chemist Joseph Black in 1755; he observed that magnesia gave rise to a soluble sulfate, whereas that derived from lime was known to be insoluble. In 1774 Carl Wilhelm Scheele, the Swedish chemist who discovered oxygen, found that the mineral called heavy spar or barys (Greek: heavy) contained a new earth, which became known as baryta (barium oxide). A further earth, strontia (strontium oxide), was identified by the London chemists Adair Crawford and William Cruickshank in 1790 on examining a mineral (strontium carbonate) found in a lead mine at Strontian in Argyllshire, Scotland.

Beryllia (beryllium oxide) was extracted from the mineral beryl and recognized as an earth by the French analytical chemist Nicolas-Louis Vauquelin in 1798. Though at first confused with alumina (aluminum oxide) because both dissolve in alkali, beryllia was shown to be distinct; unlike alumina, it reprecipitated when the alkaline solution was boiled for some time. Beryllia was originally called glucina (Greek glykys, sweet) because of its sweet taste. (This etymological root is retained in France, where the element beryllium is also known as glucinium.)

Magnesium, calcium, strontium, and barium--elements derived from alkaline earths--were isolated as impure metals by Sir Humphry Davy in 1808 by means of the electrolytic method he had previously used for isolating the alkali metals potassium and sodium. The alkaline-earth metals were later produced by reduction of their salts with free alkali metals, and it was in this way (the action of potassium on beryllium chloride) that beryllium was first isolated by the German chemist Friedrich Wöhler and the French chemist Antoine Bussy independently in 1828. Radium was discovered in 1898 by means of its radioactivity by Pierre and Marie Curie, who separated it from barium.

Most barium compounds are produced from the sulfate via reduction to the sulfide. Barium sulfate (BaSO4), a white, heavy powder that occurs in nature as the mineral barite, is one of the most insoluble salts known. It is widely used as a filler (e.g., in paper and rubber) and finds an important appliCATion as an opaque medium in the X-ray examination of the gastrointestinal tract. Lithopone, a mixture of barium sulfate and zinc sulfide, is a brilliant white pigment.

A number of uses of barium compounds depend on the ready formation of the highly insoluble sulfate. Thus the compound barium carbonate (BaCO3), perhaps the most important barium compound, is employed in removing sulfate from salt brines before they are fed into electrolytic cells (for the production of chlorine and alkali). The carbonate also is used to make other barium chemicals, as a flux in ceramics, and in the manufacture of optical glass, fine glassware, and ceramic permanent magnets for loudspeakers. Although barium carbonate is not soluble in water, it dissolves in the hydrochloric acid of the stomach and thus is used in rat poisons.

Another barium compound, barium chloride (BaCl22H2O), consisting of colourless crystals that are soluble in water, is utilized in heat-treating baths, in laboratories as a chemical reagent to precipitate soluble sulfates, and on a commercial scale with sodium sulfate to form a white filler and pigment (blanc fixe) for leather, rubber, cloth, and photographic paper. The oxygen compound barium peroxide (BaO2) is used for both oxygen production and as a source of hydrogen peroxide. Volatile barium compounds impart a yellowish green colour to a flame owing to the emission of light of mostly two characteristic wavelengths. Barium nitrate, formed with the nitrogen-oxygen group NO-3, and chlorate, formed with the chlorine-oxygen group ClO-3, are used for this effect in green signal flares and fireworks.

atomic number 56 atomic weight 137.34 melting point 725 C boiling point 1,640 C specific gravity 3.5 (20C) valence 2 electronic config. 2-8-18-18-8-2 or (Xe)6s2

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