The fluoride, SmF 3 .H 2 O, was prepared by H.
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.
Trans., 1869, p. 173) by decomposing the double fluoride of hydrogen and potassium, at a red heat in a platinum retort fitted with a platinum condenser surrounded by a freezing mixture, was having a platinum receiver luted on.
Its most important property is that it rapidly attacks glass, reacting with the silica of the glass to form gaseous silicon fluoride, and consequently it is used for etching.
- Potassium fluoride, KF, is a very deliquescent salt, crystallizing in cubes and having a sharp saline taste, which is formed by neutralizing potassium carbonate or hydroxide with hydrofluoric acid and concentrating in platinum vessels.
The hydrated fluoride, CrF3.9H20, obtained by adding ammonium fluoride to cold chromic sulphate solution, is sparingly soluble in water, and is decomposed by heat.
The component lines of a band spectrum do not as a rule give the Zeeman effect, and this seems to be connected with their freedom from pressure shifts, for when Dufour had shown that the bands of the fluoride of calcium were sensitive to the magnetic field, R.
With the exception of the fluoride, these substances are readily soluble in water and arc deliquescent.
The fluoride is found native as sellaIte, and the bromide and iodide occur in sea water and in many mineral springs.
Early in 1855 John Percy suggested that cryolite should be more convenient, as it was a natural mineral and might not require purification, and at the end of March in that year, Faraday exhibited before the Royal Institution samples of the metal reduced from its fluoride by Dick and Smith.
Of the simple compounds, only the fluoride is amenable to electrolysis in the fused state, since the chloride begins to volatilize below its melting-point, and the latter is only 5° below its boiling-point.
Cryolite is not a safe body to electrolyse, because the minimum voltage needed to break up the aluminium fluoride is 4.0, whereas the sodium fluoride requires only 4.7 volts; if, therefore, the current rises in tension, the alkali is reduced, and the final product consists of an alloy with sodium.
It has been found, however, that molten cryolite and the analogous double fluoride represented by the formula Al 2 F 6.2NaF are very efficient solvents of alumina, and that these solutions can be easily electrolysed at about 800° C. by means of a current that completely decomposes the oxide but leaves the haloid salts unaffected.
Grabau patented a method of reducing the simple fluoride of aluminium with sodium, and his process was operated at Trotha in Germany.
Minet took out patents for electrolysing a mixture of sodium chloride with aluminium fluoride, or with natural or artificial cryolite.
As a part of the voltage is consumed in the latter duty, only the residue can be converted into chemical work, and as the theoretical voltage of the aluminium fluoride in the cryolite is 4.0, provided the bath is kept properly supplied with alumina, the fluorides are not attacked.
On treatment with silver fluoride it yields nitrosyl fluoride, NOF (0.
Stannous Fluoride, SnF 2, is obtained as small, white monoclinic tables by evaporating a solution of stannous oxide in hydrofluoric acid in a vacuum.
Stannic Fluoride, SnF 4, is obtained in solution by dissolving hydrated stannic oxide in hydrofluoric acid; it forms a characteristic series of salts, the stannofluorides, M 2 SnF 6, isomorphous with the silico-, titano-, germanoand zirconofluorides.
The refractive indices of all glasses at present available lie between 1.46 and 1 90, whereas transparent minerals are known having refractive indices lying considerably outside these limits; at least one of these, fluorite (calcium fluoride), is actually used by opticians in the construction of certain lenses, so that probably progress is to be looked for in a considerable widening of the limits of available optical materials; possibly such progress may lie in the direction of the artificial production of large mineral crystals.
Silicon fluoride, SiF4, is formed when silicon is brought into contact with fluorine (Moissan); or by decomposing a mixture of acid potassium fluoride and silica, or of calcium fluoride and silica with concentrated sulphuric acid.
Whilst with sodium hydroxide, sodium fluoride is produced: 3SiF4= 4KHO = S102+ 2K 2 SiF 6 + 2H 2 0; SiF 4 + 4NaOH = SiO 2 + 4NaF+ 2H 2 O.
Silicofluoric acid, H2SiF6, is obtained as shown above, and also by the action of sulphuric acid on barium silicofluoride, or by absorbing silicon fluoride in aqueous hydrofluoric acid.
The anhydrous acid is not known, since on evaporating the aqueous solution it gradually decomposes into silicon fluoride and hydrofluoric acid.
They have been obtained artificially by Hautefeuille by the interaction of titanium fluoride and steam.
It may be obtained crystalline by fusing the anhydrous chloride with a large excess of potassium hydrogen fluoride or by heating the amorphous variety to redness with an excess of an alkaline chloride.
The amorphous metal also results when the chloride is heated with sodium; the oxide reduced with magnesium; or when fused potassium zircono fluoride is electrolysed (Wedekind, Zeit.
Troost produced crystallized zirconium by fusing the double fluoride with aluminium in a graphite crucible at the temperature of melting iron, and extracting the aluminium from the melt with hydrochloric acid.
For its extraction from zircon the mineral is heated and quenched in water to render it brittle, and then reduced to a fine powder, which is fused with three to four parts of acid potassium fluoride in a platinum crucible.
The double fluoride is decomposed with hot concentrated sulphuric acid; the mixed sulphate is dissolved in water; and the zirconia is precipitated with ammonia in the cold.
Thus the sulphate constitutes the minerals anhydrite, alabaster, gypsum, and selenite; the carbonate occurs dissolved in most natural waters and as the minerals chalk, marble, calcite, aragonite; also in the double carbonates such as dolomite, bromlite, barytocalcite; the fluoride as fluorspar; the fluophosphate constitutes the mineral apatite; while all the more important mineral silicates contain a proportion of this element.
Whereas calcium chloride, bromide, and iodide are deliquescent solids, the fluoride is practically insoluble in water; this is a parallelism to the soluble silver fluoride, and the insoluble chloride, bromide and iodide.
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.
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 rod in the mouth of the tube, the water apparently gelatinizes owing to the decomposition of the silicon fluoride formed.
Cryolite, a fluoride of aluminium and sodium, is extensively mined in Greenland and elsewhere for industrial purposes.
The fluoride, NaF, is sparingly soluble in water (I part in 25).
It forms the acid fluoride KHF 2 when dissolved in aqueous hydrofluoric acid, a salt which at a red heat gives the normal fluoride and hydrofluoric acid.
The fluoride, CrF3, results on passing hydrofluoric acid over the heated chloride, and sublimes in needles.
Cryolite (A1F 3.5NaF) is a double fluoride of aluminium and sodium, which is scarcely known except on the west coast of Greenland.
Cobalt fluoride, CoF 2.2H 2 0, is formed when cobalt carbonate is evaporated with an excess of aqueous hydrofluoric acid, separating in rose-red crystalline crusts.
Electrolysis of a solution in hydrofluoric acid gives cobaltic fluoride, CoF3.
Boron fluoride BF 3 was first prepared in 1808 by Gay Lussac and L.
Boron fluoride also combines with ammonia gas, equal volumes of the two gases giving a white crystalline solid of composition BF 3 NH 3 i with excess of ammonia gas, colourless liquids BF 3.2NH 3 and BF 3.3NH 3 are produced, which on heating lose ammonia and are converted into the solid form.
Several halogen compounds of sulphur are known, the most stable of which is sulphur fluoride, SF 6, which was first prepared by H.
Thionyl fluoride, SOF 21 has been obtained as a fuming, gas by decomposing arsenic fluoride with thionyl chloride (Moissan and Lebeau, Corn pt.
A masterly device, initiated by him, was to collect gases over mercury instead of water; this enabled him to obtain gases previously only known in solution, such as ammonia, hydrochloric acid, silicon fluoride and sulphur dioxide.
In the same year as Klaproth detected uranium, he also isolated zirconia or zirconium oxide from the mineral variously known as zircon, hyacinth, jacynth and jargoon; but he failed to obtain the metal, this being first accomplished some years later by Berzelius, who decomposed the double potassium zirconium fluoride with potassium.
In 1824 he obtained zirconium from potassium zirconium fluoride; the preparation of (impure) titanium quickly followed, and in 1828 he obtained thorium.
Balard completed for many years Berzelius's group of " halogen " elements; the remaining member, fluorine, notwithstanding many attempts, remained unisolated until 1886, when Henri Moissan obtained it by the electrolysis of potassium fluoride dissolved in hydrofluoric acid.
This salt gives the corresponding chloride and fluoride with hydrochloric and hydrofluoric acids, and the phosphate, Pb(HP04)2, with phosphoric acid.
Lead fluoride, PbF2, is a white powder obtained by precipitating a lead salt with a soluble fluoride; it is sparingly soluble in water but readily dissolves in hydrochloric and nitric acids.
A chlorofluoride, PbC1F, is obtained by adding sodium fluoride to a solution of lead chloride.
It is then dissolved in hydrofluoric acid and heated in order to expel silicon fluoride; finally the columbium, tantalum and titanium fluorides are separated by the different solubilities of their double fluorides (C. Marignac, Ann.
Columbium hydride, CbH, is obtained as a greyish metallic powder, when the double fluoride, CbF 5, 2 KF, is reduced with sodium.
With hydroflouric acid it yields uranous fluoride, UF 4, which forms double salts of the type MF UF 4.
Ruff and Curt Albert (Ber., 1905, 38, p. 53) by decomposing titanium fluoride with silicon chloroform in sealed vessels at 100 -120° C. It is a colourless gas which may be condensed to a liquid boiling at -80 2° C. On solidification it melts at about -110° C. The gas is very unstable, decomposing slowly, even at ordinary temperatures, into hydrogen,, silicon fluoride and silicon: 4SiHF 3 =2H 2 +3SiF 4 +Si.
It burns with a pale-blue flame forming silicon fluoride, silicofluoric acid and silicic acid.
Strontium fluoride, SrF 2, is obtained by the action of hydrofluoric acid on the carbonate, or by the addition of potassium fluoride to strontium chloride solution.
Zirconium fluoride, ZrF4, is obtained as glittering monoclinic tables (with 3H 2 0) by heating zirconia with acid ammonium fluoride.
Berzelius, by converting silver fluoride into silver chloride, obtained the value 19.44, and by analysing calcium fluoride the value 19.16; the more recent work of H.
557.) Titanium fluoride, TiF 4, is a fuming colourless liquid boiling at 284°, obtained by distilling a mixture of titanium oxide, fluorspar and sulphuric acid; by heating barium titanofluoride, BaTiF6 (Emrich, Monats., 1904, 25, p. 907); and by the action of dry hydrofluoric acid on the chloride (Ruff and Plato, Ber., 1904, 37, p. 673).