in physics, a fluid; or, more properly, the state of a body that was before hard or solid, but is now reduced by fusion, or fire, into a state of fluidity.

in mineralogy, a certain kind of stone which facilitates fusion. They are of different colours, purple, green, yellow, &c. more or less transparent, which are commonly found in veins of ores, and serve as the matrix to the minerals which they envelop. Most of them affect a cubical form, but others are found in lumps which have no determinate shape. They may be distinguished from other stones by the following properties.

1. They are not sufficiently hard to strike fire with steel. By this property they are distinguished from the coloured quartz-crystals called false emeralds, false rubies, &c. which names have also been improperly applied to the cubical coloured fluors.

2. They are not soluble by acids, and thus are distinguishable from calcareous spars.

3. When calcined without addition, and mixed with water, they do not form plaster; and when calcined with addition of inflammable matter, they cannot be formed into the Bolognian phosphorus. Hence they may be distinguished from the gypseous phosphoric spars and stones.

4. They are fusible by fire without addition, according to M. Engelström and M. D'Arcey.

5. They greatly facilitate the fusion of calcareous and argillaceous earths; and also of the topaz, according to Mr Pott. They are much employed in the smelting of ores, as they promote the fusion of the adhering earths.

6. When exposed to fire till they become red-hot, they emit some lucid rays in the dark; but their light is... is very weak, and afterwards they crackle and break into small pieces; whereas the gypseous phosphoric spars exposed to the same heat emit a vivid light, and then break afiinder into pieces not so pulverable as those of the heated flours.

M. Margraaf has made experiments in order to discover the nature of these stones. He ascertained the above-mentioned distinctions between them and the gypseous spars; and therefore infers, that they are not compounded of vitriolic acid with calcareous earth. He observed singular appearances on mixing them with vitriolic and other acids, and subjecting the mixtures to distillation.

Eight ounces of the powder of a green flour, being mixed with an equal weight of pure oil of vitriol, and distilled together with a graduated heat, yielded, after the watery part of the acid had passed, a fine white sublimate, which arose and adhered to the neck of the retort, and even passed into the receiver. The first parts of this sublimate which arose, appeared like butter of antimony; and, like this butter, they melted by the heat of a live coal, brought near the neck of the retort: but the parts which arose towards the end of the operation, with the greatest degree of heat, could not be melted by that heat. The retort being broken, a residuum was found weighing 12 oz. Hence 4 oz. of oil of vitriol remained united with the spar. The bottom of the retort was observed to be pierced with holes. Lastly, the liquor, which had passed into the receiver, and the white sublimate, had very sensibly a sulphurous smell. The sublimate, triturated a long time in a mortar with hot distilled water, dissolved, and passed through a filter. To the filtrated liquor some fixed alkali being added, a precipitate was formed; which being well washed and dried, was readily melted by fire into a mass resembling porcelain. The same excellent and accurate chemist produced the same effects upon this stone, by substituting, instead of the vitriolic acid, the nitrous, marine, phosphoric, or the concentrated acetic acids.

Fluor Acid. See Chemistry, no 263.

Fluor Albus, or White. See (the Index subjoined to) Medicine.