Chemical elements
  Chromium
    Isotopes
    Energy
    Occurrence
    Preparation
    Physical Properties
    Chemical Properties
    Alloys
    Amalgams
    Compounds
      Chromous Fluoride
      Chromic Fluoride
      Chromyl Fluoride
      Chromous Chloride
      Chromic Chloride
      Oxychlorides
      Chromyl Chloride
      Trichromyl Chloride
      Chromium Chlorate
      Chromium Perchlorate
      Chromous Bromide
      Chromic Bromide
      Complex Halogen-halides
      Chromous Iodide
      Chromic Iodide
      Chromium Iodate
      Chromous Oxide
      Chromo-chromic Oxides
      Chromic Oxide
      Chromic Hydroxide
      Barium Chromite
      Cadmium Chromite
      Calcium Chromite
      Cobalt Chromite
      Cupric Chromite
      Cuprous Chromite
      Ferrous Chromite
      Lithium Chromite
      Magnesium Chromite
      Manganese Chromite
      Zinc Chromite
      Chromium Dioxide
      Chromium Trioxide
      Aluminium Chromate
      Ammonium Chromate
      Ammonium Lithium Chromate
      Ammonium Potassium Chromate
      Ammonium Sodium Chromate
      Ammonium Dichromate
      Ammonium Fluochromate
      Barium Chromate
      Barium Dichromate
      Barium Potassium Trichromate
      Beryllium Chromate
      Bismuth Chromate
      Bismuth Potassium Chromates
      Cadmium Chromate
      Cadmium Dichromate
      Cadmium Trichromate
      Caesium Chromate
      Caesium Dichromate
      Calcium Chromate
      Calcium Dichromate
      Cobalt Chromate
      Cobalt Dichromate
      Copper Chromates
      Cupric Dichromate
      Gold Chromates
      Iron Chromates
      Ferric Chromate
      Ferric Ammonium Chromate
      Lead Chromate
      Basic Lead Chromates
      Lead Dichromate
      Lithium Chromate
      Lithium Chlorochromate
      Magnesium Chromates
      Manganese Chromates
      Mercuric Chromate
      Mercuric Dichromate
      Nickel Chromate
      Nickel Dichromate
      Potassium Chromate
      Potassium Dichromate
      Potassium Trichromate
      Potassium Tetrachromate
      Potassium Fluochromate
      Potassium Chlorochromate
      Rubidium Dichromate
      Silver Chromate
      Silver Dichromate
      Sodium Chromate
      Sodium Dichromate
      Sodium Trichromate
      Sodium Chlorochromate
      Stannic Chromate
      Strontium Chromate
      Strontium Dichromate
      Strontium Trichromate
      Thallous Chromate
      Thallic Chromate
      Thallous Dichromate
      Thallous Trichromate
      Thallous Chlorochromate
      Uranyl Chromate
      Zinc Chromate
      Zinc Dichromate
      Zinc Trichromate
      Perchromic Acid
      Chromium Tetroxide Triammine
      Chromous Sulphide
      Chromium Tetrasulphide
      Chromic Sulphide
      Sodium Thiochromite
      Potassium Thiodichromite
      Chromic Sulphite
      Chromous Sulphate
      Chromic Sulphate
      Lithium Chromic Sulphate
      Sodium Chromic Sulphates
      Potassium Chromic Sulphates
      Potassium Chromium Alum
      Ammonium Chromium Alum
      Hydrazine Chromium Alum
      Sulphochromic Acid
      Chromous Selenide
      Chromic Selenide
      Chromic Selenite
      Chromium Nitrides
      Chromium Azide
      Chromic Nitrate
      Chromium Monophosphide
      Chromium Sesquiphosphide
      Chromic Hypophosphite
      Chromous Orthophosphate
      Chromic Orthophosphates
      Chromous Metaphosphate
      Chromic Metaphosphate
      Chromic Pyrophosphate
      Ammonium Chromi-pyrophosphate
      Potassium Chromi-pyrophosphate
      Sodium Chromi-pyrophosphate
      Chromous Thiophosphite
      Chromous Thiopyrophosphite
      Chromous Thiopyrophosphate
      Chromous Arsenide
      Chromium Sesqui-arsenide
      Chromic Arsenite
      Chromic Arsenate
      Chromium Pyroarsenate
      Chromic Thioarsenite
      Chromium Chlorantimonate
      Chromium Orthoantimonichloride
      Tetrachromium Carbide
      Pentachromium Dicarbide
      Tetrachromium Dicarbide
      Chromium Tungsten Carbide
      Chromous Carbonate
      Ammonium Chromous Carbonate
      Potassium Chromous Carbonate
      Sodium Chromous Carbonate
      Chromic Carbonates
      Chromium Thiocarbonate
      Chromous Cyanide
      Chromic Cyanide
      Potassium Chromocyanide
      Hydrogen Chromicyanide
      Ammonium Chromicyanide
      Lithium Chromicyanide
      Sodium Chromicyanide
      Potassium Chromicyanide
      Cobaltous Chromicyanide
      Cupric Chromicyanide
      Lead Chromicyanide
      Manganous Chromicyanide
      Mercury Chromicyanide
      Nickel Chromicyanide
      Silver Chromicyanide
      Zinc Chromicyanide
      Chromous Thiocyanate
      Chromic Thiocyanate
      Chromithiocyanic Acid
      Ammonium Chromithiocyanate
      Sodium Chromithiocyanate
      Potassium Chromithiocyanate
      Barium Chromithiocyanate
      Silver Chromithiocyanate
      Lead Chromithiocyanate
      Chromium Ferrocyanide
      Trichromium Silicide
      Dichromium Silicide
      Trichromium Disilicide
      Chromium Disilicide
      Chromium Aluminium Silicide
      Sodium Chromisilicates
      Chromium Silicofluoride
      Chromium Boride
      Trichromium Diboride
      Chromous Borate
      Chromic Borate
    Detection
    Estimation
    PDB 1huo-9icc

Chromyl Chloride, CrO2Cl2






Chromyl Chloride, CrO2Cl2, sometimes termed chlorochromic acid, is readily prepared by distilling a mixture of fused potassium chromate or dichromate and sodium chloride with concentrated sulphuric acid:

3K2CrO4 + 6NaCl + 12H2SO4 = 6KHSO4 + 6NaHSO4 + 3CrO2Cl2 + 6H2O,

and, in order to remove free chlorine, repeatedly fractionating the distillate over mercury in a current of carbon dioxide. It is more expeditiously obtained, however, by dissolving chromic anhydride, CrO3, in concentrated hydrochloric acid, and adding excess of concentrated sulphuric acid, when chromyl chloride is formed, which sinks to the bottom and may readily be separated. After aspirating dry air through the liquid in order to remove dissolved hydrochloric acid, it is subjected, as before, to fractional distillation. Other methods of formation are: (a) by heating together two equivalents of chromic chloride and three of chromic anhydride, or equal parts of the latter and ferric chloride; (b) by passing hydrogen chloride over chromic anhydride; (c) by heating together phosphorus pentachloride and either chromic anhydride or potassium dichromate; (d) by the action of chlorine or hydrochloric acid upon the sesquioxide; (e) by heating together dry powdered chromic acid, acetyl chloride, and a little glacial acetic acid in carbon tetrachloride solution. It is also produced by heating a chlorochromate with sulphuric acid, or by heating the oxychloride (CrO2)5Cl6.

Chromyl chloride is a dark red, mobile liquid, of mean density 1.9587 at 0° C. It boils at 116.63° C. under 760 mm. pressure, and the solid melts at -96.5±0.5° C. It has been suggested for use as an ebulliscopic solvent, and gives a constant of 55 with chromic anhydride. Its yellowish-red vapour, which absorbs all the light from a luminous source except a narrow band in the red, has a density at temperatures up to 200° C. of 5.35 (air = l) corresponding to the formula CrO2Cl2.

Chromyl chloride fumes in air owing to the fact that it is decomposed by water into chromic and hydrochloric acids. The fumes when introduced into a Bunsen flame exhibit a characteristic spectrum. When sufficiently purified by distillation, and free from access to moisture, chromyl chloride may be kept unchanged for a considerable time, though on very long standing some dark coloured solid - probably a polymeride - is deposited. This tendency to polymerise is also suggested by the results of cryoscopic molecular weight determinations in carbon tetrachloride, tin tetrabromide, or antimony pentachloride.

When heated in a sealed tube at 180° C. for three hours, chromyl chloride is converted to chromium chlorochromate (trichromyl chloride) and chlorine, while by passing through a tube heated at 400° C., a grey or black deposit is obtained, consisting largely of the magnetic oxide, Cr5O9; at red heat the sesquioxide is formed. It readily parts with oxygen and chlorine, and is therefore an energetic oxidising and chlorinating agent, for example, towards sulphur, hydrogen sulphide, phosphorus (with explosion), hydrogen phosphide, phosphorus trichloride and oxvchloride, alcohol, turpentine, benzene and other hydrocarbons, fats, camphor, caoutchouc, and organic substances in general. In dry ammonia it burns, forming ammonium chloride and chromium dioxide. When ammonia gas is passed into a solution of chromyl chloride in acetic acid or chloroform, a slightly soluble brown substance, having the composition Cr3O6(ONH4)2, is formed. A mixture of gaseous chromyl chloride and dry chlorine passed over carbon heated to redness yields chromic chloride in a well-crystallised condition. The course of the reaction appears to be:

2CrO2Cl2 + Cl2 + 4C = 2CrCl3 + 4CO.

Chromyl chloride absorbs chlorine readily; it dissolves iodine, forming a solution which on heating yields trichromyl chloride, Cr3O6Cl2, and iodine monochloride; with an aqueous solution of potassium chloride, potassium chlorochromate is produced.

Neither bromine nor iodine forms compounds analogous to chromyl chloride under any of the conditions given above, consequently the presence of a chromate in the aqueous solution of the distillate obtained by distilling a chloride, bromide, or iodide, or a mixture of these, with potassium dichromate and concentrated sulphuric acid, is sufficient evidence of the presence of a chloride in the mixture investigated.


© Copyright 2008-2012 by atomistry.com