F L U
456
FLU
received in the u-uul maimer in glass jars standing over mercury.This gas is fluoric acid. The acid may be obtained d.ssolved inwater by luting to the retort a receiver containing water. Thedistillation is to be conducted with a very moderate heat, not onlyto allow the gas to condense, but also to prevent the tluor itselffrom subliming. After the process, provided a glass retort hasbeen employed, a crust of white earth is found in the receiver,winch has all the properties of silica. Scheele supposed that thesilica produced was formed of fluoric acid and water; and Berg-man adopted the S41110 opinion. But Wiegleb and Buccholzshewed that the quantity of silica was exactly equal to what theretort lost in weight; and Meyer c nnpleted the proof that it wasderived from the glass, by the following experiment. Me putinto each of three equal cylindrical tin vessels a mixture of threeounces of sulphuric acid and one ounce of fluor, which had beenpulverized in a mortar of metal. Into tbe first he put one ounceof pounded glass; into the second the same quantity of quartz in>owder; and into the third nothing. Above each of the vesselsle hung aspunge moistened with water, and having covered them,he exposed them to a moderate heat. The sponge in the first cy-linder was covered with the crust in half an hour; the sponge inthe second in two hours; but no crust was funned in the third,though it was exposed several days. In consequence of this deci-sive experiment, Bergman gave up his opinion; and wrote an ac-count of Meyer’s experiment to Morveau, who was employed intranslating his works, to enable him to correct the mistake in hisnotes. Soon aft< r the discovery of this acid, difficulties anddoubts concerning its existence as a peculiar acid were started bysome French chemists. To remove these objections, Mr. Scheele instituted and published a new set of experiments; which not onlycompletely established the peculiar nature of the fluoric acid, butonce more displayed the unrivalled abilities of the illustrious dis-coverer. 2. fluoric acid gas is invisible and elastic like air; itdoes not maintain combustion, nor can animals breathe it withoutdeath. It has a pungent smell, not unlike that of muriatic acid.It is heavier than common air. It corrodes the skin almost in-stantly. 3. Neither caloric nor light produces any alteration onit. 4. When water is admitted in contact with this gas, it absorbsit rapidly ; and if the gas has been obtained by means of glass ves-sels, it deposits at the same time a quantity of silica. Water ab-sorbs a considerable proportion of this gas, but the precise quan-tity has not been determined. The compound is usually termedfluoric acid by chemists. It is specifically heavier than water,has an acid taste, reddens vegetable blues, and dues not freeze tillcooled down to 23°. When heated, the acid gas is easily expel-led, except the last portions of it, which adhere with great obsti-nacy. 5. Neither oxygen gas nor any of the simple combusti-bles or incombustible* produce any change on fluoric acid, eitherin the gaseous or liquid state. 6. Fluoric acid gas does not actupon any of the metals, but liquid fluoric acid is capable of oxid-ing iron, zinc, copper, and arsenic. It does not act upon gold,platinum, silver, mercury, lead, tin, antimony, cobalt. 7. Itcombines with alkalies, earths, and metallic oxides, and forms w iththem salts which are denominated filiates. See Fi.uate. Themost singular property of fluoric acid is (lie facility with which itcorrodes glass and siliceous bodies, especially when hot, and theease with which it holds silica in solution even when in the state ofgas. This affinity for silica is so great, that the thickest glass ves-sels can only withstand its action tor a short time; ami the greatestprecautions are scarcely sufficient to obtain it entirely free fromsiliceous earth. 8. It produces no change, as far as is known, uponany of the acids already described. 9 . Its affinities are as fallows:Lime,
Strontian,
Potass,
Soda,
Ammonia,
(ilucina.
Alumina,
Zirconia,
10. As fluoric acid produces an insoluble compound with lime,it may be employed with great advantage, as Pelletier lias observ-ed, to detect the presence of that earth when held in solution. A
drop or two of the acid causes a milky cloud or precipitate to ap-pear, if any lime be present. The property which this acid iias ofcorroding glass, has induced several ingenious men to attempt, bymeans of it, to engrave, or rather etch, upon glass. The glass iscovered completely with wax; and then that part where the lettersor figures are to appear is laid bare, by removing the wax. Thewhole is then exposed for some time to the hot vapours of fluoricagid. 'Phis simple process is employed with advantage in writinglabels on glass vessels, and in graduating thermometers, and othersimilar instruments. Phe discovery is by no means new; it hasbeen shewn by Beckman and Accuni, that this quid was employedfor that purpose by Henry Swanhard, an artist of Nuremberg , asearly as lt)70. lie seems to have kept his art for some lime se-cret, but the receipt was made public by Pauli in 1725. SeeEtching on Glass.
FLUSHING, FLESSINGUF,, or VLISS1NGEN, a strongsea-port town of Holland in the island of Wab hcren, and depart-ment of the Meuse , 4miiesS.\V. of Middtelmrg, and 28 N.E. ofOstend . 'Phis town together with the whole island was annexed toFrance by an imperial decree of Dec. 27, 1809. Eat. 31° 2(5'37" N.Lon. 3°34' 9" E. from Greenwich.
FLU ST 11 A, a genus of worms of the order zoophyla. Animala polype proceeding from porous shells; stem fixed, foliaceous,membranaceous, consisting of numerous rows of cells united to-gether, and woven like a mat. There are about 18 species. Theverticillata is found in the Mediterranean, adhering to fuci.
FLUTE, [Ji.il it la,] an instrument of music, the simplest of allthose of the wind kind. It is played on by blowing it with themouth, and the tones or notes are changed by stooping and o)>en-ing the holes disposed for that purpose along its side, l he ancientfistula*, or (lutes, were made of reeds, afterwards of wood, anti lastof metal.
Flute, German, is an instrument entirely different from thecommon (lute. It is not, like that, put into the mouth to lie play-ed, but the end is stopt with a tampion, or plug, and the lower lipis applied to a hole about two indies and a half, or three inches,distant from the end. Although playing the flute is on the Con-tinent more generally practised than in Britain , yet we think ituseful to observe, that this exercise is by no means compatiblewith either young or weak lungs. Indeed, all wind-instrumentsare in many respects objectionable, because, alter blowing forci-bly, a large portion of air is suddenly .inhaled, and afterwardspartially expelled from the lungs, so that they are by this de-bilitating action continually expanded and relaxed, in a mannervery different from that which Nature pursues in the process of re-spiration.
Flute, or Fluyt , (originally perhaps.//oflt) is a kind of longvessel, with flat ribs, or floor timbers; round behind, and swelledin the middle ; serving chiefly for the carrying of provisions infleets, or squadrons of ships, though it is also used for merchandize.
FLUTES , or FLIPPINGS, in architecture, [H-rpendicularchannels, or cavities, cut along the shaft of a column, or pilaster.See Architecture.
FLUX, in medicine, an extraordinary issue, or evacuation, ofsome humours of the body. See Medicine.
Flux, in metallurgy, is sometimes used synonymously with fu-sion : for instance, an ore, or rather matter, is said to he in liquidflux, w hen it is completely fused. But the word flux is generally'used to signify certain saline matters, which facilitate the fusion ofores, and other substances which are difficultly fusible in assays,
| and in the reductions of ores. We shall here describe the fluxes! recommended by Bergman, in vol. ii. 1. l he phosphoric acid,or rather tile microcosmic salt, as it is called, which contains thatacid partly saturated with mineral, partly with ammonia, andloaded besides with much water. This salt, when exposed to theflume, boils and foams violently, with a continual crackling noise,until the water and ammonia have flown old; afterwards it is lewagitated, sending forth something like black scoria' arising from theburned gelatinous part: these, however, are soon dispelled, andexhibit a pellucid spheriele encompassed by a beautiful greencloud, whit h is occasioned by the deflagration ot the plm-phoi'tiSarising from the extrication o’f the acid liy means ot the intuann' 3 "hie matter. 'Pin* clear globule w hicli remains, upon the removalof the flame, continues longer soft than that formed hv borax, andtherefore is more til for the addition of the matter to lie dissolve"*'Phe ammonia is expelled by the fire ; llierelore an exce-s of ae'd
, '4 remain*