Galena and other lead ores are abundant in veins in the limestone, but they are now only worked on a large scale at Mill Close, near Winster; calamine, zinc blende, barytes, calcite and fluor-spar are common.
Galena and other lead ores are abundant in veins in the limestone, but they are now only worked on a large scale at Mill Close, near Winster; calamine, zinc, blende, barytes, calcite and fluor-spar are common.
Scheele had done, and because he was employing a glass vessel he got "fluor acid air" (silicon fluoride).
Calcium fluoride, CaF2, constitutes the mineral fluor-spar, and is prepared artificially as an insoluble white powder by precipitating a solution of calcium chloride with a soluble fluoride.
FLUORINE (symbol F, atomic weight iv), a chemical element of the halogen group. It is never found in the uncombined condition, but in combination with calcium as fluor-spar CaF2 it is widely distributed; it is also found in cryolite Na3A1F6, in fluor-apatite, CaF 2.3Ca 3 P 2 O 8, and in minute traces in seawater, in some mineral springs, and as a constituent of the enamel of the teeth.
The U-shaped electrolytic vessel and the electrodes are made of an alloy of platinum-iridium, the limbs of the tube being closed by stoppers made of fluor-spar, and fitted with two lateral exit tubes for carrying off the gases evolved.
The fluorine, which is liberated as a gas at the anode, is passed through a well cooled platinum vessel, in order to free it from any acid fumes that may be carried over, and finally through two platinum tubes containing sodium fluoride to remove the last traces of hydrofluoric acid; it is then collected in a platinum tube closed with fluor-spar plates.
Only one compound of hydrogen and fluorine is known, namely hydrofluoric acid, HF or H 2 F 2, which was first obtained by C. Scheele in 1771 by decomposing fluor-spar with concentrated sulphuric acid, a method still used for the commercial preparation of the aqueous solution of the acid, the mixture being distilled from leaden retorts and the acid stored in leaden or gutta-percha bottles.
Moissan, Le Fluor et ses composes (Paris, 1900).
His published works include Le four g lectrique (1897), and Le fluor et ses composes (1900), besides numerous papers in the Comptes rendus and other scientific periodicals.
Next the metal is covered with a very basic slag, made by melting lime with a little silica and fluor spar.
The substances in commonest use are: - lime or limestone, to slag off silica and silicates, fluor-spar for lead, calcium and barium sulphates and calcium phosphate, and silica for removing basic substances such as limestone.
Chlor-, brom-, iodoand fluor-benzoic acids are known and can be obtained by oxidizing the corresponding halogen toluenes, or from the amido acids, or by substitution.
FLUOR-SPAR, native calcium fluoride (CaF 2), known also as Fluorite or simply Fluor.
In France it is called fluorine, whilst the term fluor is applied to the element (F).
Name Flussspat or Fluss.) Fluor-spar crystallizes in the cubic system, commonly in cubes, either alone or combined with the octahedron, rhombic dodecahedron, four-faced cube, &c. The four-faced cube has been called the fluoroid.
Fluor-spar has a hardness of 4, so that it is scratched by a knife, though not so readily as calcite.
Fluor-spar, though cubic, sometimes exhibits weak double refraction, probably due to internal tension.
Many kinds of fluor-spar are thermo-luminescent, i.e.
Cavities containing liquid occasionally occur in crystals of fluor-spar, notably in the greasy green cubes.
A dark violet fluor-spar from Wolsendorf in Bavaria, evolves an odour of ozone when struck, and has been called antozonite.
Fluor-spar is largely employed by the metallurgist, especially in lead-smelting, and in the production of ferro-silicon and ferro-manganese.
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 Derbyshire, known locally as "Blue John," is.
Corsi, the eminent Italian antiquary, held that fluor-spar was the material of the famous murrhine vases.
Fluor-spar is a mineral of very wide distribution.
Fine yellow fluor-spar occurs in some of the Saxon mines, and beautiful rose-red octahedra are found in the Alps, near Goschenen.
Many localities in the United States yield fluor-spar, and it is worked commercially in a few places, notably at Rosiclare in southern Illinois.