BORAX. This salt is found native in some of the lakes of Thibet and Persia, and is imported from India under the name of lineal, which, after purification, forms the refined borax of commerce. Of late years borax has been obtained by combining native boracic acid with soda. Borax forms hexahedral prisms, slightly efflorescent, and requiring 20 of cold and 6 of boiling water for solution. When heated, water of crystallization is driven off, and the residuary salt fuses into what is called glass of borax.
Crystallized borax consists of 68 boracic acid + 32 soda ± 90 water. It has upon some tests an alkaline reaction, and has hence been called sub-borate of soda. Bor ax is chiefly used by workers in metals as a flux : it is also employed in medicine.
Dry borax acts on m€tallic oxides at a high temperature, melting and vitrifying them into beautiful colored glasses, on which account it is a most useful reagent with the blow-pipe. It tinges oxide of chrome, emerald green ; oxide of cobalt, intense blue ; oxide of copper, pale green ; oxide of tin, opal ; oxide of iron, bottle green ; oxide manganese, violet. In the fusion of metals it protects the surface from oxidizement, and dissolves any ox ides off the surface : hence it is an excel lent flux in the hands of the goldsmith, in soldering precious metals, and to the brazier, in soldering copper and iron.
When mixed with shell-lac, in the ratio of 1 to 5, it renders the lac soluble in wa ter, and forms with it a species of varnish. BORON. The base of boracic acid, discovered by Davy in 1807. It may be procured by heating dry boracic acid with potassium. It is a dark olive-colored substance, a nonconductor of electricity, insoluble in water, infusable, and of a specific gravity = 2, Heated to redness it burns into boracic acid, which consists of 20 boron + 48 oxygen.
Boracic acid is found in the hot springs, and amongst the volcanic products of the Lipari islands, and in the waters of Sasso in the Florentine territory ; it also occurs in some minerals. It may be obtained by adding excess of sulphuric acid to a strong solution of borax. Its specific gra
vity is 1.48. In its usual state of scaly crystals it is a hydrate, composed of 68 dry acid + 27 water. In this state it re quires about 80 parts of cold and 3 of boiling water for its solution. It dis solves in alcohol, and the solution burns with a characteristic green flame. It reddens litmus ; but renders turmeric brown, like an alkali. When its water is driven off by fusing it at a high heat, the anhydrous acid concretes into a glassy substance of the specific gravity of 1.8. It is a useful flux, and was formerly used in medicine under the name of sedative salt.
The boracic acid lagoons of Tuscany are an interesting instance of the conver sion of a natural phenomenon, which seemed only a subject of wonder, into a productive manufacture. These lagoons are depressions or mud holes in the soil, from which issue hot vapors highly im pregnated with boracic acid, which were formerly regarded with terror by the inhabitants of their vicinity, and they sought by public prayers a deliverance from this scourge. In 1818, Mr. Lan derel conceived the idea of rendering these vapors a source of profit. The la goons being situated upon the declivity of a mountain, they were surrounded by a basin of mason work, and water from the mountain stream conducted into them, so as to form a series of artificial lakes at different levels. The water is let into the upper basin, where it remains some twenty or thirty hours and becomes impregnated by the acid vapors ; at the end of this time the water is drawn off into the second basin, when it receives a further pregnation; and so on successive ly through six or eight, until it reaches the evaporating reservoirs. These are of lead, and the heat for carrying on the evaporation is obtained from the vapors themselves, which are brought in pipes below the boilers. All the means of ma nufacture are furnished by the locality itself. The annual product of these la goons is two and a half millions of pounds. The boracic acid is converted into borax by combining with soda.