The tender medullary substance which grows at the top of the great palm tree.

Bo Rax, (from the Arabic term borac). Called also chrysocolla, capistrum auri, ancinar, boraxtrion, anucar, atincar, tincal, amphitane, baurach, nitrum fac-ti!ium,santerna, and nitrum nativum. Borac signifies nitre, but it was corrupted into borax, and applied to the chrysocolla. It is not much unlike alum, and if genuine, hath a sweet taste at the first, but afterwards an unctuous one. Its pure crystals arc hexaedral prisms, terminated by three sided summits finely cut; it dissolves with difficulty in cold, but easily in boiling water; requiring of the former more than twelve times its weight. It is soluble in alcohol, swells and bubbles in the fire, and soon becomes a glass, which dissolves again in water; but if mixed with flint or sand, it becomes a durable glass, hard enough to cutcommon glass. It is an excellent flux for metals, and for their ores; 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. A solution of borax made in a menstruum of vegetable acid, when inspissated by evaporation, is a tenacious substance that will not crystallize, but will dissolve in the air. Borax was originally brought from Thibet, where it was found on the shores of a lake, seemingly the crater of an old volcano. We receive it inviscated in a greasy substance, and in an impure state, then called tincal. It has been since found more pure in the mines of Ritinquipa and Escapa, and still more pure in China. In Europe it has been discovered in a mineral lake in Tuscany. It is purified by long boiling and repeated crystallization; but when most pure, white, and transparent, it has a somewhat greasy fracture. We now know it to be a compound salt, with an exeess of alkali; containing thirty-nine parts of boracic acid, seventeen of soda, and forty-four of water. It is decomposed by barytes, magnesia, and lime.

Its acid, the sedative salt, is of a white, scaly, glittering appearance, has a cooling saline taste, and reddens the blue vegetable infusions. A pint of boiling water dissolves 183 grains, but it dissolves more easily in alcohol. Its solution in spirit is green, and burns with a green flame. If dry, it is fixed in the fire.

The borax of the shops is sometimes adulterated with alum: but then it is not so light nor clear, nor does it swell so much when put on burning coal.

Borax itself is used for soldering gold, whence its name chrysocolla. It is also a solder for other metal's; and a powerful flux for fusing minerals of all kinds. It is used to give a gloss to silks.

As a medicine it seems to possess inconsiderable virtues, or these have not been sufficiently examined. I' has been, however, styled a deobstruent, diuretic, and emmenagogue,in doses of half a drachm,or two scruples. A mixture of it with honey - viz. borax one drachm, honey one ounces - is efficacious in removing aphthous crusts from the mouth and fauces, but a solution in water is considered to possess superior power. Externally it is a far better cosmetic than bismuth. If given in powder it issaid to be emetic, but, mixed with aromatics, this quality is checked, and in the fluor albus it is supposed highly useful.

A dose of borax is from gr. v. to 31 ss.