Chemical elements
  Arsenic
      Occurrence
      Ubiquity
      History
    Isotopes
    Energy
    Production
    Application
    Physical Properties
    Chemical Properties
      Aluminium Arsenide
      Antimony Arsenides
      Barium Arsenide
      Bismuth Arsenides
      Cadmium Arsenides
      Calcium Arsenide
      Cerium Arsenide
      Chromium Arsenides
      Cobalt Arsenides
      Copper Arsenides
      Gold Arsenides
      Iridium Arsenide
      Iron Arsenides
      Lead Arsenides
      Lithium Arsenide
      Magnesium Arsenide
      Manganese Arsenides
      Mercury Arsenides
      Molybdenum Arsenide
      Nickel Arsenides
      Niobium Arsenide
      Palladium Di-arsenide
      Platinum Arsenides
      Potassium Arsenides
      Rhodium Arsenide
      Ruthenium Arsenide
      Silver Arsenides
      Sodium Arsenide
      Strontium Arsenide
      Thallium Arsenide
      Tin Arsenides
      Tungsten Arsenide
      Uranium Arsenide
      Zinc Arsenides
      Arsenic Subhydride
      Arsenic Monohydride
      Arsenic Trihydride
      Arsenic Trifluoride
      Arsenic Pentafluoride
      Arsenic Nitrosyl Hexafluoride
      Arsenic Trichloride
      Arsenic Oxychloride
      Arsenic Pentachloride
      Arsenic Tribromide
      Arsenic Oxybromide
      Arsenic Moniodide
      Arsenic Diiodide
      Arsenic Triiodide
      Arsenic Pentiodide
      Arsenic Suboxide
      Arsenious Oxide
      Aluminium Arsenite
      Ammonium Arsenites
      Antimony Arsenite
      Barium Arsenites
      Beryllium Arsenite
      Bismuth Arsenite
      Cadmium Arsenites
      Calcium Arsenites
      Chromic Arsenite
      Cobalt Arsenites
      Copper Arsenites
      Gold Arsenites
      Iron Arsenites
      Lead Arsenites
      Lithium Arsenite
      Magnesium Arsenites
      Manganese Arsenites
      Mercury Arsenites
      Nickel Arsenites
      Palladium Pyroarsenite
      Platinum Arsenites
      Potassium Arsenites
      Arsenites of Rare Earth Metals
      Rubidium Metarsenite
      Silver Arsenites
      Sodium Arsenites
      Strontium Arsenites
      Thallous Orthoarsenite
      Tin Arsenites
      Titanyl Tetrarsenite
      Tungsto-arsenites
      Uranyl Metarsenite
      Zinc Arsenites
      Zirconium Arsenite
      Arsenic Tetroxide
      Arsenic Pentoxide
      Aluminium Arsenates
      Ammonium Arsenates
      Barium Arsenates
      Beryllium Arsenates
      Bismuth Arsenates
      Cadmium Arsenates
      Caesium Arsenate
      Calcium Arsenates
      Chromium Arsenates
      Cobalt Arsenates
      Copper Arsenates
      Hydroxylamine Orthoarsenate
      Iron Arsenates
      Lead Arsenates
      Lithium Arsenates
      Magnesium Arsenates
      Manganese Arsenates
      Mercury Arsenates
      Molybdenum Arsenates
      Nickel Arsenates
      Palladium Arsenate
      Platinic Arsenate
      Potassium Arsenates
      Rare Earth Metals Arsenates
      Rhodium Arsenate
      Rubidium Arsenates
      Silver Arsenates
      Sodium Arsenates
      Strontium Arsenates
      Thallium Arsenates
      Thorium Arsenates
      Tin Arsenates
      Titanyl Arsenate
      Tungsto-arsenic Acids
      Uranium Arsenates
      Vanado-arsenates
      Zinc Arsenates
      Zirconium Arsenates
      Perarsenates
      Arsenic and Sulphur
      Arsenic Subsulphide
      Tetrarsenic Trisulphide
      Arsenic Disulphide
      Arsenic Trisulphide
      Arsenic Pentasulphide
      Thioarsenates
      Ammonium Thioarsenates
      Antimony Thioarsenate
      Barium Thioarsenates
      Beryllium Thioarsenate
      Bismuth Thioarsenate
      Cadmium Thioarsenates
      Calcium Thioarsenates
      Cerium Thioarsenates
      Chromium Thioarsenate
      Cobalt Thioarsenate
      Copper Thioarsenates
      Gold Thioarsenates
      Iron Thioarsenates
      Lead Thioarsenates
      Lithium Thioarsenates
      Magnesium Thioarsenates
      Manganese Thioarsenates
      Mercury Thioarsenates
      Molybdenum Thioarsenates
      Nickel Thioarsenates
      Platinic Thioarsenate
      Potassium Thioarsenates
      Silver Thioarsenates
      Sodium Thioarsenates
      Strontium Thioarsenates
      Thallium Orthothioarsenate
      Tin Thioarsenates
      Uranyl Thioarsenate
      Yttrium Thioarsenate
      Zinc Thioarsenates
      Zirconium Thioarsenate
      Trioxythioarsenic Acid
      Dioxydithioarsenic Acid
      Oxytrithioarsenic Acid
      Arsenic Monosulphatotrioxide
      Arsenic Disulphatotrioxide
      Arsenic Trisulphatotrioxide
      Arsenic Tetrasulphatotrioxide
      Arsenic Hexasulphatotrioxide
      Arsenic Octasulphatotrioxide
      Complex salts of Sulphato-compounds of Arsenic
      Arsenic Nitride
      Arsenic Imide
      Arsenic Amide
      Arsenic Phosphides
      Arsenic oxyphosphides
      Arsenic Phosphate
      Arsenic Thiophosphate
      Arsenic Tricarbide
      Arsenic Pentasilicide
      Boron Arsenate
    Detection of Arsenic
    Estimation of Arsenic
    Physiological Properties
    PDB 1b92-1ihu
    PDB 1ii0-1tnd
    PDB 1tql-2hmh
    PDB 2hx2-2xnq
    PDB 2xod-3htw
    PDB 3hzf-3od5
    PDB 3ouu-9nse

Arsenic Trifluoride, AsF3






Arsenic Trifluoride, AsF3, is formed when fluorine reacts with arsenic trichloride or with the arsenides of the alkali or alkaline earth metals; by the action of anhydrous hydrofluoric acid or of acid fluorides on arsenious oxide; by the action of certain metallic fluorides, for example silver or lead fluoride on arsenic trichloride, or of ammonium fluoride on arsenic tribromide; and by the action of iodine pentafluoride on arsenic.

The usual method of preparation is that employed by Dumas, who first discovered the compound in 1826, namely, by the addition of concentrated sulphuric acid (2 parts) to a mixture (1 part) containing equal weights of calcium fluoride and arsenious oxide. The trifluoride is collected in a lead receiver immersed in ice water and rectified by distillation on a water-bath at 65° C. It is best kept in a platinum bottle.

Arsenic trifluoride is a colourless mobile liquid with an odour resembling that of silicon tetrafluoride. It fumes in air owing to its rapid reaction with water vapour (see below). A drop on the skin evaporates rapidly, leaving a painful burn similar to that produced by hydrofluoric acid. According to Thorpe, the density at 0° to 4° C. is 2.6659 and at the boiling point 2-4497, the latter temperature being 60.4° C. Earlier workers gave b.pt. 63° to 64° C. The liquid solidifies to a crystalline mass at -8.5° C. The volume change on heating is expressed by the equation

vθ = v0(1 + 0.001443θ + 0.000000297θ2)

The heat of formation of liquid arsenic trifluoride has been obtained indirectly by determining the heats of dissolution of the trifluoride and of a mixture of arsenious oxide and sodium fluoride in about one litre of normal sodium hydroxide solution. The value obtained was 198,300 calories. Assuming Trouton's constant to be 21, the heat of vaporisation is about -7000 calories, so that the heat of formation of gaseous arsenic trifluoride is 191,300 calories.

The molecular volume in the liquid and gaseous states has been measured and from the results the radii of the atoms constituting the molecule have been calculated.

The liquid is a poor conductor of electricity, but some decomposition due to electrolysis occurs, a gas which attacks platinum being liberated and arsenic deposited on the cathode.

The Raman spectrum of arsenic trifluoride consists of four lines with the following frequencies: w1(1)707, W2(1)341, w3(2)644, and w4(2)274 cm.-1; a pyramidal molecule is indicated.

The trifluoride readily reacts with water, and a trace of the latter is sufficient to cause the liquid to show an acid reaction. If more water be added there is a slight heating effect and, according to Dumas, hydrofluoric and arsenious acids are formed. Berzelius concluded that hydrofluoarsenic acid was the product. The solution reacts with tin and zinc and also attacks glass. The liquid trifluoride itself when heated in a glass vessel readily attacks the latter, thus:

4 AsF3 + 3SiO2 = 2As2O3 + 3SiF4

Admixture of the trifluoride with alcohol or ether, or with fixed or volatile oils, causes some decomposition. Ammonia readily combines to form a white powder, arsenic triamminotrifluoride, As(NH3)3F3; this compound is decomposed by water. Phosphine reacts differently, yielding hydrogen fluoride:

AsF3 + PH3 = AsP + 3HF

With the chlorides of phosphorus there is an interchange of halogens, thus -

AsF3 + PCl3 = AsCl3 + PF3
5 AsF3 + 3PCl5 = 5AsCl3 + 3PF5

and this is also the case with silicon tetrachloride, thionyl chloride and thiophosphoryl chloride, thus:

4AsF3 + 3SiCl4 = 4AsCl3 + 3SiF4
2AsF3 + 3SOCl2 = 2AsCl3 + 3SOF2
AsF3 + PSCl3 = AsCl3 + PSF3

Sulphur chloride and carbon tetrachloride do not react in the cold. Silico-chloroform at ordinary temperature reacts vigorously, two simultaneous reactions apparently taking place:

(i) AsF3 + SiHCl3 = AsCl3 + SiHF3
(ii) 4AsF3 + 3SiHCl3 = 2AsCl3 + 3SiF3 + 3HCl + 2As

Arsenic trifluoride reacts with bromine to form a crystalline substance; iodine dissolves in the liquid yielding a purple-red solution; the nature of these products has not been elucidated.


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