Barium, one of the metallic elements. The mineral known as heavy spar was first mentioned in 1602 by an Italian cobbler of Bologna, Vincenzio Cascariolo, who discovered that when this mineral was fused with resin and charcoal it became phosphorescent. The Bologna phosphorescing stone, or lapis Solaris, soon became famous all over Europe, and marvellous cures were sometimes attributed to it. The true composition of the heavy spar was not known till 1760, when Marggraf showed that it contained sulphur. That the mineral contained an earth was first made known by Scheele and Gahn in 1774. Berzelius, and almost simultaneously Pontin and Davy, obtained in 1808 an amalgam of barium, which Davy subsequently decomposed by distillation and thus isolated the metal. More recently Bunsen and Matthiessen have prepared barium from the fused chloride by means of electrolysis. Bergman introduced the word heavy spar, terra ponderosa, and Guyton de Mor-veau substituted the Greek heavy, from which he derived the word barote, which was afterward changed to baryta, while the metal was called barium. - For the preparation of barium, anhydrous chloride of barium is mixed with sal ammoniac and fused in a Hessian crucible. A small porcelain crucible is then filled with the fused mass, and so attached to the poles of a battery of six Bunsen's cups as to be readily decomposed when brought to a state of fusion. The barium is obtained in a fine brass-yellow powder, which must be stored under naphtha, as it oxidizes rapidly in the air and decomposes water at all temperatures. Alloys of barium with bismuth, tin, and aluminum have been prepared; they are crystalline, and decompose water at all temperatures, but have no application in the arts. The compounds of barium are numerous, and have extensive use in medicine, chemistry, and technology. The oxide has been employed as a substitute for lime in the manufacture of glass, also to prevent the fermentation of the molasses of sugar cane. The binoxide has been proposed as an agent for the manufacture of oxygen from the atmosphere.
If the protoxide be heated in a tube and a current of air be passed over it, it absorbs oxygen, which it again gives up on raising the temperature. It was at one time thought that the process could be made continuous, but experience has shown that the baryta melts and refuses to take up more oxygen. This can in a measure be prevented by previously mixing it with manganese dioxide and soda. By adding concentrated sulphuric acid to the binoxide of barium and gently warming, oxygen gas in the form of ozone is liberated. - As the native sulphate of baryta is generally too impure to be used directly in the arts, it is fused with charcoal and resin or oil, and the pure white sulphate obtained from the dissolved residue by the addition of sulphuric acid. Thus prepared, sulphate of baryta is used as a permanent white, under the name of Mane fixe, in the manufacture of paper, as a white pigment, and to adulterate white lead. As the specific gravity of heavy spar ranges from 4.3 to 4.7, it is frequently mistaken for the ore of copper or lead. Blanc fixe hardens when mixed with soluble glass, and is therefore capable of use in fresco painting. It is also used in making brilliant white satin paper. - Chloride of barium can be readily made by dissolving the native carbonate in hydrochloric acid.
It is a valuable reagent in the laboratory for the detection of sulphuric acid, and in medicine as a remedy in scrofulous complaints. Several cases of poisoning by means of this agent are on record. The chloride and the oxalate are manufactured into anti-incrustation powders. A very good blasting powder is made of the nitrate of baryta, which, being much cheaper than the ordinary nitre powder, has long been employed in mines and on public works in Europe. It is not considered so dangerous as common powder, and, although slow in action, is found to be effective enough for all practical purposes. - Baryta salts are used in Belgium in the preparation of citric acid, tartaric acid, and hydrocyanic acid. In the manufacture of alum it has been found that the aluminate of baryta can be very readily prepared by fusion, from which alumina salts can be easily separated. This method is employed in France, in making alum from bauxite. Prussian blue, made from potash salts, can be prepared in a ready and cheap way through the intervention of cyanide of barium. Chromic acid is more cheaply prepared by the aid of baryta than in any other way. Stearic acid, from which adamantine candles are made, can be combined with and afterward easily separated from this substance.
Baryta is also used in the preparation of starch sirup, so frequently sold as liquid honey; spirits of hartshorn or ammonia; a beautiful yellow paint, often employed as a substitute for chrome yellow, on account of its. delicacy of tone and cheapness; soap, and an infinite number of other substances. Some of the best English plate glass has been made by substituting carbonate of baryta for carbonate of soda. It is a clear crystal sheet, and not liable to atmospheric changes. This glass has also been found to be admirably adapted for optical instruments. The soluble salts of baryta are poisons, the readiest antidote being sulphate of soda or magnesia.