Borax

Borax, or BIBORATE OF SODA, is found native as a saline incrustation on the shores of certain lakes in Persia, Tibet, Nevada, and California, but it also occurs widely scattered over the world. It has been long known, but it was not till 1732 that its chemical nature was ascertained. At first, and till comparatively recent years, the main source was the crude article brought from Tibet in skins, and going by the name of tincal. As so obtained, the crystals were coated with a greasy matter, said to be derived from the skins, and this had to be first removed by means of soda before the borax could be refined. In 1856 the Californian sources of borax were discovered, the bottom of a lake being found to be covered to a depth of about 18 inches with a mud impregnated with borax, and containing large crystals of it. From this mud, by treatment with hot water and crystallisation, there is first obtained concentrated borax, and by further treatment this yields the refined borax. In other places in California the borax is found mixed with sand in a light granular form, containing about $\backslash frac\{1\}\{3\}$th of the pure salt, while large crystalline masses of it occur below the surface of the ground. In all these cases a similar method of purification is adopted. The importance of these deposits may be gathered from the figures showing the production of borax in the Pacific States—viz. in 1872, 280,000 lb.; in 1876, 5,140,000 lb.; and in 1884, 3,732,000 lb. In Europe, large quantities of artificial borax are prepared from the Boracic Acid (q.v.) of Tuscany. This, mixed with carbonate of soda, is heated in a furnace, carbonic acid being liberated, and the crude salt is then dissolved in water to free it from impurities, and crystallised. The changes which take place in this operation are represented by the following equation:

The common variety of borax contains ten equivalents of water, $\backslash text\{Na\}\_2\backslash text\{B\}\_4\backslash text\{O\}\_7\; +\; 10\backslash text\{H\}\_2\backslash text\{O\}$, and forms prismatic crystals; but another variety exists, known as octahedral borax, and containing only five molecules of water. Borax is soluble in twelve times its weight of cold water, and in half its weight of boiling water, yielding a clear solution with a slightly sweetish taste. It is of great use in the chemical arts owing to its properties of dissolving metallic oxides, and of forming a flux when heated with other substances. On this account it is much used in connection with the Blowpipe (q.v.), before which it yields different coloured glasses corresponding to the metals present. It is also employed in the manufacture of enamel, and for glazing or coating vessels in pottery, as also in the formation of the paste for artificial gems. To the metallurgist it is an aid in the readiness with which it promotes the fusion of metallic mixtures, and the separation of the metals; and to the solderer it is of service in forming a thin glassy coating over the edges of the metals, which prevents their oxidation at the time they are being joined together. It is used as a mordant in calico-printing, while as an adjunct to, or substitute for, soap in washing, it gives satisfactory results in the proportion of $\backslash frac\{1\}\{2\}$ lb. to 10 gallons of water. For the toilet, borax in solution is invaluable, making in itself an admirable shampoo, while its utility for cleaning brush and comb are well known. A varnish prepared by boiling together one part of borax and five of shellac with water is used for stiffening hats; and as an insecticide it is very powerful, being specially destructive to cockroaches. For preserving meat, fish, butter, and milk, either alone, or along with Boracic Acid (q.v.), borax has a wide application, no less than 20,000 lb. having been supplied to the Chicago canning works in one year for the preserving of meat alone. Besides these technical uses, borax is much used in medicine as an antiseptic, being applied either in powder or as lotion. For ulcerating surfaces, and in the treatment of the infantile disease thrush, it is extensively applied; while throat lozenges, designed to relieve the hoarseness of public speakers, generally contain this valuable salt as a constituent.