Borax Pharm. Lond. & Edinb. Borax: a crystalline salt; very difficultly soluble in cold water; swelling and bubbling up in the fire, and changing into a light white spongy friable matter, which, doon subsiding on a continuance of the fire, melts into a substance resembling glass, but which is still found to be dissoluble in water, though more difficultly than the borax at first.

(a) Mem. de l'acad. roy. de scienc. de Paris, pour l'ann. 1734.

It is brought from the East Indies in a very impure state; consisting partly of large bexae-dral prismatic flatted crystals, but chiefly of smaller and more irregular ones, partly whitish and partly green, joined together as it were into one lump by a fetid greasy, or oily, yellow substance; intermingled with sand, small stones, and other impurities. Of its origin and preparation we have no certain account.

This impure borax was formerly refined at Venice, afterwards in Holland only, and now by some particular persons in England also, into large irregular colourless masses, in appearance resembling alum. The salt is commonly called tincal in its rough state, and borax when-thus purified or refined. The method of refining it is kept a secret. Certain additional matters are suspected to be employed; the common refined borax being different in some respects, particularly in its power of vitrefying earthy bodies, from the crystals unrefined or simply purified by solution.

The purer crystals of tincal, or refined borax, dissolve, by boiling, in a small quantity of water, so as in cooling to concrete almost all into a solid mass, only a very little liquid remaining on the top: to keep them dissolved in the cold, more than fourteen times their weight of water is necessary. On boiling the impure tincal in water, the oil dissolves along with the salt into a soapy liquid; from whence it may be presumed that the oily matter is not of a mineral, but of a vegetable or animal origin. From this solution it is very difficult to separate the oil, without additions which alter the quality of the salt: but if the rough tincal be previously heated in an iron ladle, or other convenient vessel, till it ceases to bubble and flame, the oil is destroyed or made indissoluble, and boiling water extracts from the black mass only the pure borax.

Pure borax has a sweetish somewhat pungent taste, leaving in the mouth an impression like that of alkaline salts, but far milder. Like alkaline salts also, it changes the colour of blue flowers to green, precipitates earthy and metallic bodies dissolved in acids, and renders vegetable and animal oils miscible with water: it does not, however, sensibly effervesce with acid any more than with alkaline liquors. It dissolves in acids more easily than in water, and promotes likewise the solution of some vegetable acid salts of themselves difficultly dissoluble. A mixture of borax with twice its weight of tartar dissolves in about one sixth part of the quantity of water that would be necessary for their solution separately: the liquor tastes acid, like tartar by itself, and deposites a considerable quantity of tartar in cooling. About equal parts of the two form a compound perfectly neutral, in taste more like borax than tartar, which is kept dissblved by five times its weight of water a little above freezing. On infpiffation, a viscous tenacious mass is left, which does not crystallize, and which deliqui-ates in the air. Borax affords also glutinous compounds with all the other acids except the vitriolic: saturated solutions even of the borax by itself are considerably so.This salt appears to consist of the mineral alkali or basis of sea salt, united with a smaller proportion of a peculiar saline subacid concrete. By all the mineral acids, and, as is said, by the acetous, its constituent parts are separable from one another; the acid uniting with the alkaline basis, and disjoining therefrom the subacid ingredient of the borax.

This analysis is most commodiously effected by the vitriolic acid. A mixture of nine parts of borax, three of oil of vitriol, and one of water, being urged, in a wide-necked retort, with a fire, at first gentle and afterwards pretty hastily increased till the vessel becomes red hot; the subacid salt of the borax, called seda-tive salt, rises into the neck, and concretes into thin shining white plates. But as this salt proves volatile only while moist, a part of it remains behind, and may be sublimed, like the first, by pouring back on the residuum the liquor that distills, and renewing the operation. The same salt may be obtained more commodiously, though scarcely in so pure a state, by adding the oil of vitriol to the borax dissolved in water, and, after due evaporation, setting the mixture to shoot: the sedative salt cry-stallizes on the surface, much sooner than the other saline matter, into thin plates; which, uniting together, and growing heavier, fall to the bottom. The salt, which in either case remains after the separation of the sedative salt, is a combination of the vitriolic acid with the alkaline basis of the borax, and has not been observed to differ from the common combination of that acid with the alkaline basis of sea salt, that is, from the sal mirabile or cathartic salt of Glauber. The sedative salt, joined to the marine alkali, recomposes borax again.

Sal. sedativ. Ph. Paris.

The peculiar and characteristic ingredient of the borax, though called subacid from its property of neutralizing alkalies, scarcely discovers any other mark of acidity. Its taste is bitterish, accompanied with a flight impression of coolness. It makes no change in the colour of blue flowers, and no effervescence with alkalies or with acids. It melts in a moderately strong fire, and assumes a perfect vitreous appearance; but this apparent glass, as well as the salt itself, may be totally sublimed, if repeatedly moistened, by a less degree of heat; and totally, though difficultly, dissolved both by water and by rectified spirit.

It is observable, that the spirituous solution of the sedative salt, set on fire, burns with a green flame; and that borax itself, boiled in spirit, is partially dissolved, and tinges its flame of the same colour. Perhaps it is principally, or solely, this salt, that the spirit extracts from the borax; for spirit burnt on the alkali of borax, exhibits no greenness.

Borax is accounted an efficacious deobstruent, diuretic, emmenagogue, and promoter of delivery. Its virtues have not as yet been thoroughly ascertained by experience, and are by many questioned; the borax having generally been given in conjunction with other substances, to which the effects, experienced from the compound, may be, in part at least, attributed. That the borax itself however, has really some virtues of this kind, may be presumed from the effects it has been observed to produce when used in large quantity: Trioen relates, that an ounce and a half of borax having been taken by a young woman in mistake for cream of tartar, an uterine hemorrhage succeeded, so profuse, that life was despaired of: the flux was got under by medicines; but the ill state of health, and almost universal oedema, which followed it, were lasting (a). Solution of borax has been found to be a powerful dissolvent of aphthous crusts in the mouth and fauces of children (b).

The peculiar saline concrete, extricated from borax by acids, is supposed to be antispasmodic and anodyne, whence its name sedative salt. It is said to calm the heat of the blood in burning fevers, to prevent or remove delirious symp-toms, and allay, for a time, melancholical, hypochondriacal, and hysterical complaints. It continues in some esteem in France, where it was first discovered by Mr. Homberg, but has never come into practice among us. Its dole is from three grains to a scruple.