BARIUM from Gk. I3aptis, barys, heavy; alluding to its high specific gravity). A metallic element isolated in 1808 by Sir Hum phry Davy. It is not found native, but occurs chiefly as the sulphate in barite, as the carbonate in witherite, and in other minerals of a more complex composition; also in mineral Waters, the ashes of certain plants, and in sea-water. Metallic barium was first obtained by Davy, who decomposed its hydrate with a powerful voltaic battery, and obtained an amalgam of barium and mercury. The mercury of the amal,gant was ex pelled by heating in an iron crucible. The metal itself (symbol. Ba: atomic weight, 137.43) was described by Davy as 'silver-white,' and by Bunsen as 'golden-yellow,' in color, so that it is questionable as to whether chemically pure barium has ever been obtained. It is a slightly lustrous, somewhat malleable metal, which melts at a red heat, but cannot be distilled. its spe cific gravity is from 3.5 to 4.
The compounds of barium are used for a vari ety of purposes. its peroxide, BaO,,„ formed when the anhydrous monoxide is heated to a dull red heat in a stream of oxygen, is used in the manufa•ture of peroxide of hydrogen. Barium peroxide, may, further, be used as a bleaching agent as well as for preparing oxygen.
The monoxide of barium, called baryta. is found, in combination with carbonic acid, as the mineral witherite, and in combination with sul phuric acid as the mineral barite. or heavy spar. It is prepared commercially by heating barium nitrate in a porcelain crucible or retort. or by igniting barium carbonate in the strong heat of a forge fire. It is a grayish white, extremely caustic, poisonous, and strongly alkaline mass, which finds its chief application in suga•-relin ing, as it forms an almost insoluble compound with sugar when added to molasses or other sac cha•ine solutions. Baryta unites readily with water to form barium hydroxide.
Barium sulphate, the most important of the commercial salts of barium, is found native as the mineral barite or barytes - (also called eawk, cask or caulk). It is found in England, as in Derbyshire and Shropshire; also in Eu rope, and in the United States at various locali ties. but chiefly in Missouri. Tennessee, North Carolina. and Virginia. It is a heavy, white
mineral, with a specific gravity of 4.4S, and is found crystallizing in the orthorhombic system, and massive. The better grades are used in the manufacture of pigments, as a cheap substitute for, or as an adulterant of, white lead; in manu facturing reagents, and in pyrotechny: also as a makeweight in the paper manufactures: while the lower grades are used by pork-packers in the preparation of canvas for their products. Barium sulphate was an important constituent of the white body used by 'Wedgwood in his jasper-ware. It is made artificially by adding dilute sulphuric acid to a solution of barium chloride; the resulting white precipitate. after being well washed and dried, constituting the pig ment called blow. fixe. or permanent while. In 1S19, 41,894 short tons of barytes, valued at 8139,528, were produced in the 'United States.
Barium chloride, made by treating the native carbonate. witherite, with hydrochloric• acid, is used in chemistry as a reagent, in thepreparation of the artificial sulphate or permanent white, and for preventing incrustation in boilers.
Barium nitrate is prepared commercially by dissolving the native carbonate in dilute nitric acid crystallizing the barium nitrate. It is largely used in pyroteelmy, in the preparation of green fires, and in the manufacture of explo sive compounds, as a substitute for potassium nitrate.
Barium salts, when brought into a non-lumi nous flame, burn with a yellowish-green color. BAR'JE'SUS. See ELYMAS.
BARK (akin to Sw. and Dan. bark, LG. borke: possibly related to AS. beo•gan, Ger. be•gen, to cover). In the stems of perennial woody plants, the portion which lies outside the wood. and can be easily separated from it, par Oeularly at certain times. The term is also often applied to the corresponding part of annual stems, especially to those which contain textile fibres, such as flax, hemp, etc. But this is more properly called the cortex (q.v.), and the word 'bark' should he used only of shrubs and trees. European and English botanists, and con sequently English translations of foreign works, use the term 'bark' for the dead and dry outer portions only of what is known in this country as bark.