Lond. Boras Sod2e, Edin. Dub. Bi-borate of Soda.1

The term borax is a corruption of the Arabic word buruk, which signifies brilliant. Vide Asiatic Researches, 8vo. vol. iii. p. 255,

Syn. Borate alcalinule de Soude (F.), Borax (G.), Borace (I.), Borrax(S.), Tineal (Portuguese), Buruk (Arab.), Tancana (San.), Sohaga (H.), Valligarum (Tarn.), Patteric (Malay), Tunkav (Pers.), Pigar (Jav.)

This is the purified state of a natural salt found in Persia and Thibet. In the latter country it is formed in the bed of a lake situated among the mountains, fifteen days' journey from Tisolumboo, which is twenty miles in circumference, and supplied only by springs from the bottom.1 The borax is dug in large masses from the edges and shallows of the lake; yet the quantity is not diminished, the cavities being gradually filled by a fresh deposition of the salt. In this state it is named tineal, and is brought home packed in chests, in masses of adhering crystals, of a grey yellowish, or greenish white colour, intermixed with sand and other impurities, and covered with a greasy artificial production to prevent it from efflorescing. The purification of tincal was first discovered by the Venetians; and afterwards long carried on by the Dutch, who kept the process secret. Pelletier has ascertained, that, by destroying the unctuous matter by calcination, the salt may be obtained pure by solution and crystallization.2 His method has been practised in England, but at present scarcely any tincal is imported, and the greater part of the borax used in England is made by saturating the boracic acid, procured" from the vapour springs of Volterra, near Leghorn 3, with carbonate of soda.

Qualities. - Purified bi-borate of soda is inodorous, and has a styptic, cool, alkalescent taste. It is of a white colour, and usually in irregular, crystalline masses, approaching to the form of hexangular prisms, terminated by triangular pyramids. It effloresces slowly and very slightly in the air; dissolves in twelve times its weight of water at 60° of Fahr., and in twice its weight of boiling water; the solution changing the vegetable blues to green. In a moderate heat it undergoes the watery fusion, loses four tenths of its weight, and becomes a dry, white, spongy mass, without undergoing any decomposition. According to Bergman, 100 parts consist of 34 acid, 17 soda, and 49 water1; or 2 equivalents of boracic acid (34.9 + 2) = 69.8 + 1 of soda = 31.3 + 10 of water - 90, making the equivalent of the salt 191.1. It is decomposed by the majority of the acids; by potash, and the sulphates, hydrochlorates, phosphates, and fluates of the earths, and of ammonia.

1 Saunders, Phil. Trans, vol. lxxix. p. 97.

2 Memoires de Chimie, vol. i. p. 82.

3 The following is the method of making the acid at Volterra. A cavity or basin is dug round the openings whence the vapour issues, and a small stream of water conducted into it: but as soon as the basin is filled the stream is turned aside. The vapour is condensed in the water of the basin, and the heat, which it evolves, aiding the spontaneous evaporation of the water, this gradually becomes a concentrated solution of boracic acid, and is transferred to leaden troughs in which it is farther concentrated by the assistance of fire. The solution is then put into casks, on the sides of which the boracic acid is deposited in crystals, which are collected, and, without any further purification, are brought to market.

Medical properties and uses. - This salt is refrigerant and detergent. I have given it internally, in aphthous affections, and in excessive salivation, with much advantage; and it is a useful topical application when mixed with honey, in aphtha of the mouth.

Officinal preparation.-Mel Boracis, L. E.D.