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tube being closed by stoppers made of fluor-spar, and fitted with two lateral exit tubes for carrying off the gases evolved. Whilst the. electrolysis is proceeding, the apparatus is kept at a See also:

CONSTANT, BENJAMIN (1845-1902)

constant temperature of – 23° C. by means of liquid methyl chloride. The fluorine, which is liberated as a See also:

gas at the anode, is passed through a well cooled platinum vessel, in See also:

order to See also:

FREE

free it from any acid fumes that may be carried over, and finally through two platinum tubes containing See also:

SODIUM [symbol Na, from Lat. natrium; atomic weight 23.00 (0=16)]

sodium fluoride to remove the last traces of hydrofluoric acid; it is then collected in a platinum tube closed with fluor-spar plates. B. Brauner (Jour. Chem. See also:

Soc., 1894, 65, p. 393) obtained fluorine by See also:

HEATING

heating potassium fluorplumbate 3KF•HF•PbF4.

At 200° C. this See also:

salt decomposes, giving off hydrofluoric acid, and between 230–250° C. fluorine is liberated. Fluorine is a See also:

PALE (through Fr. pal, from Lat. palms, a stake, for paglus, from the stem pag- of pangere, to fix; " pole " is from the same original source)

pale greenish-yellow gas with a very See also:

sharp See also:

SMELL (connected etymologically with " smoulder " and " smoke ")

smell; its specific gravity is 1.265 (H. Moissan); it has been liquefied, the liquid also being of a yellow See also:

COLOUR (Lat. color, connected with celare, to hide, the root meaning, therefore, being that of a covering)

colour and boiling at -187° C. It is the most active of all the chemical elements; in contact with See also:

HYDROGEN [symbol H, atomic weight x-oo8 (0=16)]

hydrogen combination takes See also:

PLACE (through Fr. from Lat. platea, street; Gr. IrAar6s, wide)

place between the two gases with explosive violence, even in the dark, and at as See also:

low a temperature as -21o° C.; finely divided See also:

CARBON (symbol C, atomic weight 12)

carbon See also:

burns in the gas, forming carbon tetrafluoride; water is decomposed even at See also:

ORDINARY (med. Lat. ordinarius, Fr. ordinaire)

ordinary temperatures, with the formation of hydrofluoric acid and " ozonised " See also:

OXYGEN (symbol 0, atomic weight 16)

oxygen; See also:

IODINE (symbol I, atomic weight '26.92)

iodine, See also:

SULPHUR

sulphur and See also:

PHOSPHORUS (Gr. 4ws, light, sPEpety, to bear)

phosphorus melt and then inflame in the gas; it liberates See also:

CHLORINE (symbol Cl, atomic weight 35`46 (0=16)

chlorine from chlorides, and combines with most metals instantaneously to See also:

FORM (Lat. forma)

form fluorides; it does not, however, combine with oxygen. Organic compounds are rapidly attacked by the gas. Only one See also:

compound of hydrogen and fluorine is known, namely hydrofluoric acid, HF or H2F2, which was first obtained by C. See also:

SCHEELE, KARL WILHELM (1742-1786)

Scheele in 1771 by decomposing fluor-spar with concentrated sulphuric acid, a method still used for the commercial preparation of the aqueous See also:

SOLUTION (from Lat. solvere, to loosen, dissolve)

solution of the acid, the mixture being distilled from leaden retorts and the acid stored in leaden or See also:

GUTTA (Latin for " drop ")

gutta-percha bottles. The perfectly anhydrous acid is a very volatile colour-less liquid and is best obtained, according to G. See also:

Gore (Phil. Trans., 1869, p. 173) by decomposing the See also:

double fluoride of hydrogen and potassium, at a red See also:

HEAT (0. E. haktu, which like " hot," Old Eng. hat, is from the Teutonic type haita, hit, to be hot; cf. Ger. hitze, heiss; Dutch, hitte, heet, &c.)

heat in a platinum See also:

RETORT (Lat. retorquere, to twist or turn back)

retort fitted with a platinum See also:

CONDENSER

condenser surrounded by a freezing mixture, and having a platinum See also:

RECEIVER

receiver luted on. It can also be prepared in the anhydrous condition by passing a current of hydrogen over dry See also:

SILVER

silver fluoride.

The pure acid thus obtained is a most dangerous substance to handle, its vapour even when highly diluted with See also:

air having an exceedingly injurious See also:

ACTION

action on the See also:

RESPIRATORY

respiratory See also:

ORGANS

organs, whilst inhalation of the pure vapour is followed by See also:

DEATH

death. The anhydrous acid boils at 19°.5 C. (H. Moissan), and on cooling, sets to a solid See also:

mass at -102°•5 C., which melts at–92°•3 C. (K. Olszewski, Monats. See also:

FUR (connected with O. Fr. forre, a sheath or case; so " an outer covering ")

fur Chemie, 1886, 7, p. 371). Potassium and sodium readily dissolve in the anhydrous acid with See also:

EVOLUTION

evolution of hydrogen and formation of fluorides. The aqueous solution is strongly acid to See also:

LITMUS (apparently a corruption of lacmus, Dutch lacmoes, lac, lac, and moes, pulp, due to association with " lit," an obsolete word for dye, colour; the Ger. equivalent is Lac/emus, Fr tournesol)

litmus and dissolves most metals directly. Its most important See also:

PROPERTY

property is that it rapidly attacks See also:

glass, reacting with the See also:

SILICA

silica of the glass to form gaseous See also:

SILICON [symbol Si, atomic weight 28.3 (0= 16)]

silicon fluoride, and consequently it is used for See also:

ETCHING (Dutch, etsen, to eat)

etching. T. E.

See also:

Thorpe (Jour. Chem. Soc., 1889, 55, p. 163) determined the vapour See also:

DENSITY (Lat. densus, thick)

density of hydrofluoric acid at different temperatures, and showed that there is no approach to a definite value below about 88° C. where it reaches the value 10.29 corresponding to the molecular See also:

formula HF; at temperatures below 88° C. the value increases rapidly, showing that the See also:

MOLECULE (from mod. Lat. molecula, the diminutive of moles, a mass)

molecule is more complex in its structure. (For references see J. N. Friend, The Theory of See also:

VALENCY

Valency (1909), p. III.) The aqueous solution behaves on concentration similarly to the other halogen -acids; E. Deussen (Zeit. anorg. Chem., 1905, 44, pp. 300, 408; 1906, 49, p. 297) found the solution of constant boiling point to contain 43.2% HF and to See also:

BOIL

boil at IIo° (75o mm.).

The salts of hydrofluoric acid are known as fluorides and are easily obtained by the action of the acid on metals or their oxides, hydroxides or See also:

CARBONATES

carbonates. The fluorides of the See also:

ALKALI

alkali metals, of silver, and of most of the heavy metals are soluble in water; those of the alkaline earths are insoluble. A characteristic property of the alkaline fluorides is their See also:

POWER [WILLIAM GRATTAN] TYRONE (1797-1841)

power of combining with a molecule of hydrofluoric acid and with the fluorides of the more electro-negative elements to form double fluorides, a behaviour not shown by other metallic halides. Fluorides can be readily detected by their power of etching glass when warmed with sulphuric acid; or by warming them in a glass tube with concentrated sulphuric acid and holding a moistened glass See also:

rod in the mouth of the tube, the water apparently gelatinizes owing to the decomposition of the silicon fluoride formed. The atomic weight of fluorine has been determined by the See also:

con-version of calcium, sodium and potassium fluorides into the corresponding sulphates. J. See also:

BERZELIUS, JONS JAKOB (1779-1848)

Berzelius, by converting silver fluoride into silver chloride, obtained the value 19.44, and by analysing calcium fluoride the value 19.16; the more See also:

RECENT

recent See also:

WORK

work of H. Moissan gives the value 19.05. See H. Moissan, Le Fluor et ses composes (See also:

Paris, 1900). FLUOR-SPAR, native calcium fluoride (CaF2), known also as FLUORITE or simply FLUOR. In See also:

France it is called fluorine, whilst the See also:

TERM

term fluor is applied to the element (F).

All these terms, from the See also:

Lat. fluere, " to flow," recall the fact that the spar is useful as a See also:

FLUX (Lat. fluxus, a flowing; this being also the meaning of the English term in medicine, &c.)

flux in certain metallurgical operations. (Cf. its Ger. name Flussspat or Fluss.) Fluor-spar crystallizes in the cubic See also:

SYSTEM

system, commonly in cubes, either alone or combined with the See also:

OCTAHEDRON (Gr. 6K-rw, eight, Mpa, base)

octahedron, rhombic See also:

DODECAHEDRON (Gr. Melia, twelve, and ESpa, a face or base)

dodecahedron, four-faced See also:

CUBE (Gr. K46os, a cube)

cube, &c. The four-faced cube has been called-the fluoroid. In fig. 1, a is the cube (See also:

LOO (formerly called " Lanterloo," Fr. lanturlu, the refrain of a popular 17th-century song)

loo), d the rhombic dodecahedron (11o), and f the four-faced cube (310). Fig. 2 shows a characteristic twin of interpenetrant cubes. The crystals are sometimes polysynthetic, a large octahedron, e.g., being built up of small cubes. The faces are often etched or corroded. Cleavage is nearly always perfect, parallel to the octahedron. Fluor-spar has a hardness of 4, so that it is scratched by a See also:

KNIFE (0. E. cuff, a word appearing in different forms in many Teutonic languages, cf. Du. knijf, Ger. Kneif, a shoe-maker's knife, Swed. knif; the ultimate origin is unknown; Skeat finds the origin in the root of " nip," formerly " knip "; Fr. canif is a

knife, though not so readily as See also:

CALCITE

calcite. Its specific gravity is about 3.2.

The colour is very variable, and often beautiful, but the mineral is too soft for See also:

PERSONAL

personal decoration, though it forms a handsome material for vases, &c. In some fluor-spar the colour is disposed in bands, regularly following the See also:

CONTOUR

contour of the crystal. As the colour is usually expelled, or much altered, by heat, it is believed to be due to an organic pigment, and the presence of See also:

HYDROCARBONS

hydrocarbons has been detected in many specimens by G. Wyrouboff, and other observers. H. W. See also:

MORSE, SAMUEL FINLEY BREESE (1791—1872)

Morse (Prot. Amer. Acad., 1906, p. 587)obtained carbon monoxide and dioxide, hydrogen and See also:

NITROGEN [symbol N., atomic weight 14.01, 0=16]

nitrogen and small quantities of oxygen from Weardale specimens by heating. He concluded that the gases are due to the decomposition of an organic colouring See also:

MATTER

matter, which has, however, no connexion with the See also:

FLUORESCENCE

fluorescence or thermo-luminescence of the mineral. Certain crystals from See also:

Cumberland are beautifully fluorescent, appearing See also:

PURPLE

purple with a bluish See also:

INTERNAL

internal haziness by reflected See also:

LIGHT

light, and greenish by transmitted light.

Fluor-spar, though cubic, sometimes exhibits weak double See also:

refraction, probably due to internal tension. Many kinds of fluor-spar are thermo-luminescent, i.e. they glow on exposure to a moderate heat, and the name of chlorophane has been given to a variety which exhibits a See also:

green glow. The mineral also phosphoresces under the See also:

Rontgen rays. Cavities containing liquid occasionally occur in crystals of fluor-spar, notably in the greasy green cubes of Weardale in See also:

Durham. A dark See also:

VIOLET

violet fluor-spar from WSlsendorf in See also:

BAVARIA (Ger. Bayern)

Bavaria, evolves an odour of See also:

OZONE

ozone when struck, and has been called antozonite. Ozone is also emitted by a violet fluor-spar from Quincie, dep. See also:

Rhone, France. In both cases the spar evolves free fluorine, which ozonizes the air. Fluor-spar is largely employed by the metallurgist, especially in See also:

lead-smelting, and in the See also:

PRODUCTION (Lat. productionem, from producere, to pro-duce)

production of ferro-silicon and ferro-See also:

MANGANESE (symbol Mn; atomic weight, 54.93 (0=16)], a metallic chemical element. Its dioxide (pyrolusite)

manganese. It is also used in See also:

IRON [symbol Fe, atomic weight 55.85 (0=16)]

iron and See also:

brass foundries, and has been found useful as a flux for certain See also:

gold-ores and in the reduction of See also:

ALUMINIUM (symbol Al; atomic weight 27.0)

aluminium. It is used as a source of hydrofluoric acid, which it evolves when heated with sulphuric acid. The mineral is also used in the production of See also:

OPAL

opal glass and enamel See also:

WARE

ware.

In consequence of its low refractive and dispersive power, colourless pellucid fluor-spar is valuable in the construction of apochromatic lenses, but this variety is rare. The dark violet fluor-spar of See also:

DERBYSHIRE

Derbyshire, known locally as " See also:

BLUE (common in different forms to most European languages)

Blue See also:

John," is prized for ornamental purposes. It occurs almost exclusively at See also:

TRAY

Tray Cliff, near See also:

CASTLETON

Castleton. The dark purple spar, called by the workmen " See also:

bull See also:

BEEF (through O. Fr. boef, mod. boeuf, from Lat. bos, bovis, ox, Gr. f3oiir, which show the ultimate connexion with the Sanskrit go, gaits, ox, and thus with " cow")

beef," may be changed, by heat, to a See also:

rich amethystine tint. Being very brittle, the spar is rather difficult to work on the See also:

LATHE

lathe, and is often toughened by means of See also:

RESIN (through O.Fr. resine, modern reline, from Lat. resina, prcbably Latinized from Greek Pirivrt, resin)

resin. F. Corsi, the eminent See also:

ITALIAN

Italian See also:

ANTIQUARY

antiquary, held that fluor-spar was the material of the famous murrhine vases. Fluor-spar is a mineral of very wide See also:

DISTRIBUTION (Lat. distribuere, to deal out)

distribution. Some of the finest crystals occur in the lead-See also:

VEINS

veins of the Carboniferous See also:

LIMESTONE

Limestone See also:

SERIES (a Latin word from serere, to join)

series in the See also:

north of See also:

England, especially at Weardale, Allendale and See also:

Alston See also:

MOOR

Moor. It is also found in the lead and See also:

COPPER (symbol Cu, atomic weight 63.1, H=1, or 63.6, O = 16)

copper-mines of See also:

CORNWALL

Cornwall and S. See also:

DEVON, EARLS OF

Devon, notably near See also:

LISKEARD

Liskeard, where See also:

FINE

fine crystals have been found, with faces of the six-faced octahedron replacing the corners of the cube. In Cornwall fluor-spar is known to the miners as " cann." Fine yellow fluor-spar occurs in some of the Saxon mines, and beautiful See also:

rose-red octahedra are found in the See also:

ALPS

Alps, near Goschenen.

Many localities in the See also:

UNITED

United States yield fluor-spar, and it is worked commercially in a few places, notably at Rosiclare in See also:

SOUTHERN

southern See also:

ILLINOIS

Illinois.

End of Article: FLUORINE (symbol F, atomic weight 19)

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