Amorphous silicon likewise burns with great energy in fluorine.
ACTION OF FLUORINE UPON METALS.
Sodium and potassium combine with fluorine with great vigor at ordinary temperatures, becoming incandescent, and forming their respective fluorides, which may be obtained crystallized from water in cubes. Metallic calcium also burns in fluorine gas, forming the fused fluoride, and occasionally minute crystals of fluorspar. Thallium is rapidly converted to fluoride at ordinary temperatures, the temperature rising until the metal melts and finally becomes red hot. Powdered magnesium burns with great brilliancy. Iron, reduced by hydrogen, combines in the cold with immediate incandescence, and formation of an anhydrous, readily soluble, white fluoride. Aluminum, on heating to low redness, gives a very beautiful luminosity, as do also chromium and manganese. The combustion of slightly warmed zinc in fluorine is particularly pretty as an experiment, the flame being of a most dazzling whiteness. Antimony takes fire at the ordinary temperature, and forms a solid white fluoride. Lead and mercury are attacked in the cold, as previously described, the latter with great rapidity. Copper reacts at low redness, but in a strangely feeble manner, and the white fumes formed appear to combine with a further quantity of fluorine to form a perfluoride. The main product is a volatile white fluoride. Silver is only slowly attacked in the cold. When heated, however, to 100°, the metal commences to be covered with a yellow coat of anhydrous fluoride, and on heating to low redness combination occurs, with incandescence, and the resulting fluoride becomes fused, and afterward presents a satin-like aspect. Gold becomes converted into a yellow deliquescent volatile fluoride when heated to low redness, and at a slightly higher temperature the fluoride is dissociated into metallic gold and fluorine gas.
The action of fluorine on platinum has been studied with special care. It is evident, in view of the corrosion of the positive platinum terminal of the electrolysis apparatus, that nascent fluorine rapidly attacks platinum at a temperature of -23°. At 100°, however, fluorine gas appears to be without action on platinum. At 500°-600° it is attacked strongly, with formation of the tetrafluoride. PtF4, and a small quantity of the protofluoride, PtF2. If the fluorine is admixed with vapor of hydrofluoric acid, the reaction is much more vigorous, as if a fluorhydrate of the tetrafluoride, perhaps 2HF.PtF4, were formed. The tetrafluoride is generally found in the form of deep-red fused masses, or small yellow crystals resembling those of anhydrous platinum chloride. The salt is volatile and very hygroscopic. Its behavior with water is peculiar. With a small quantity of water a brownish yellow solution is formed, which, however, in a very short time becomes warm and the fluoride decomposes; platinic hydrate is precipitated, and free hydrofluoric acid remains in solution. If the quantity of water is greater, the solution may be preserved for some minutes without decomposition. If the liquid is boiled, it decomposes instantly. At a red heat platinic fluoride decomposes into metallic platinum and fluorine, which is evolved in the free state. This reaction can therefore be employed as a ready means of preparing fluorine, the fluoride only requiring to be heated rapidly to redness in a platinum tube closed at one end, when crystallized silicon held at the open end will be found to immediately take fire in the escaping fluorine. The best mode of obtaining the fluoride of platinum for this purpose is to heat a bundle of platinum wires to low redness in the fluorspar reaction tube in a rapid stream of fluorine. As soon as sufficient fluoride is formed on the wires, they are transferred to a well stoppered dry glass tube, until required for the preparation of fluorine.
ACTION OF FLUORINE UPON NON-METALLIC COMPOUNDS.
Sulphureted Hydrogen.—When the horizontal tube shown in Fig. 3 is filled with sulphureted hydrogen gas and fluorine is allowed to enter, a blue flame is observed on looking through the fluorspar windows playing around the spot where the fluorine is being admitted. The decomposition continues until the whole of the hydrogen sulphide is converted into gaseous fluorides of hydrogen and sulphur.
Sulphur dioxide is likewise decomposed in the cold, with production of a yellow flame and formation of fluoride of sulphur.
Hydrochloric acid gas is also decomposed at ordinary temperatures with flame, and, if there is not a large excess of hydrochloric acid present, with detonation. Hydrofluoric acid and free chlorine are the products.
Gaseous hydrobromic and hydriodic acids react with fluorine in a similar manner, with production of flame and formation of hydrofluoric acid. Inasmuch, however, as bromine and iodine combine with fluorine, as previously described, these halogens do not escape, but burn up to their respective fluorides. When fluorine is delivered into an aqueous solution of hydriodic acid, each bubble as it enters produces a flash of flame, and if the fluorine is being evolved fairly rapidly there is a series of very violent detonations. A curious reaction also occurs when fluorine is similarly passed into a 50 per cent. aqueous solution of hydrofluoric acid itself, a flame being produced in the middle of the liquid, accompanied by a series of detonations.
Nitric acid vapor reacts with great violence with fluorine, a loud explosion resulting. If fluorine is passed into the ordinary liquid acid, each bubble as it enters produces a flame in the liquid.