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Fluorine
The name of the element is derived from the Latin (fluo = I flow). Fluorspar (calcium fluoride, CaF2) was known in the middle ages as a flux in metallurgical processes. Hydrogen fluoride HF, was produced by the action of concentrated sulphuric acid on fluorspar in the eighteenth century, but all chemical methods devised to produce the free element failed. The electrolysis of an aqueous solution of hydrogen fluoride, first attempted by Davy, gave hydrogen and oxygen. It was not until 1886 that Moissan electrolysed anhydrous hydrofluoric acid (containing potassium hydrogen fluoride, KHF2, to render it considering) and obtained fluorine at the anode. This process is still the only effective one for preparing fluorine.
Occurrence
Calcium fluoride occurs as fluorspar or fluorite in England, e.g. in Derbyshire, where it is coloured blue and in the United States. The usually colourless crystals show a blue fluorescence when heated and the name for this phenomenon clearly originates from this property. Other minerals containing fluorine are cryolite, Na3AlF6 (used in the extraction of aluminium) and fluorapatite, CaF2.3Ca3(PO4)2. Bones and teeth contain fluorides, and some natural waters contain traces.
Preparation
Fluorine cannot be prepared directly by chemical methods, and the only method of preparing it is by electrolysis of a fused fluoride. This may be carried out either (a) using fused potassium hydrogen fluoride, KHF2 in a cell heated electrically to 250-300˚C or (b) using fused electrolyte of composition KF:HF = 1:2 in a cell at 70-100˚C, which can be electrically or steam heated.
Process (b) at the lower temperature is commonly used both in the laboratory and on the large scale, and the essentials of the electrolytic cell are similar in each case. Figure shows such a cell, which can be made of steel, or a copper-nickel ally (‘Monel’ metal): the cell forms the cathode and the anode is of amorphous carbon. During electrolysis =, fluorine is liberated at the anode at the cathode and is similarly collected. The hydrogen fluoride content of the fused electrolyte is maintained is almost pure, containing only a little hydrogen fluoride, which is removed by passage of the gas over sodium fluoride:
NaF + HF
NaHF2
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Occurrence
Calcium fluoride occurs as fluorspar or fluorite in England, e.g. in Derbyshire, where it is coloured blue and in the United States. The usually colourless crystals show a blue fluorescence when heated and the name for this phenomenon clearly originates from this property. Other minerals containing fluorine are cryolite, Na3AlF6 (used in the extraction of aluminium) and fluorapatite, CaF2.3Ca3(PO4)2. Bones and teeth contain fluorides, and some natural waters contain traces.
Preparation
Fluorine cannot be prepared directly by chemical methods, and the only method of preparing it is by electrolysis of a fused fluoride. This may be carried out either (a) using fused potassium hydrogen fluoride, KHF2 in a cell heated electrically to 250-300˚C or (b) using fused electrolyte of composition KF:HF = 1:2 in a cell at 70-100˚C, which can be electrically or steam heated.
Process (b) at the lower temperature is commonly used both in the laboratory and on the large scale, and the essentials of the electrolytic cell are similar in each case. Figure shows such a cell, which can be made of steel, or a copper-nickel ally (‘Monel’ metal): the cell forms the cathode and the anode is of amorphous carbon. During electrolysis =, fluorine is liberated at the anode at the cathode and is similarly collected. The hydrogen fluoride content of the fused electrolyte is maintained is almost pure, containing only a little hydrogen fluoride, which is removed by passage of the gas over sodium fluoride:
NaF + HF
NaHF2Services:- Fluorine Homework | Fluorine Homework Help | Fluorine Homework Help Services | Live Fluorine Homework Help | Fluorine Homework Tutors | Online Fluorine Homework Help | Fluorine Tutors | Online Fluorine Tutors | Fluorine Homework Services | Fluorine
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Inorganic Chemistry
Organic Chemistsry
Analytical Chemistry
Biochemistry
Physical Chemistry
Topics
Aluminium
Aluminium Compounds
Aluminium Properties
Ammonia
Amorphous Preparation Properties
Antimony
Arsenic
Arsenic Compounds
Atomic Structure
Atomic Theory
Beryllium
Bismuth
Bisulphites And Sulphites
Boron
Boron Compounds
Calcium
Calcium Compounds
Carbon
Carbon Compounds
Chlorine
Covalent Bond Modern Theory
Deuterium
Diamond
Fluorine
Fuels
Graphite
Hydrogen Peroxide
Hydrogen Properties
Hydrogen Sulphide
Hydrogen-Discovery, Occurrence
Hydrogen-Industrial Preparation
Lead
Lead Compounds
Lithium, Rubidium, Caesium
Magnesium
Magnesium Compounds
Nitric Acid
Nitrogen
Nitrogen Dioxide
Oxides
Oxygen
Ozone
Phosphine
Phosphorus
Phosphorus Pentachloride
Potassium
Potassium Compounds
Silicon
Silicon Compounds
Sodium
Sodium Carbonate
Sodium Chloride
Sodium Hydride, Peroxide
Sodium Hydroxide
Sodium Hydroxide Properties
Sodium Properties
Strontium And Barium
Sulphides
Sulphur
Sulphur Dioxide
Sulphuric Acid
Tin
Tin Compounds
Valency Description
Valency Electronic Theory
Water
Water Purification
Water Softening Methods
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