Chemical elements
  Potassium
    Isotopes
    Energy
    Preparation
    Physical Properties
    Chemical Properties
      Potassium hydride
      Potassium fluoride
      Potassium hydrogen fluoride
      Potassium chloride
      Potassium bromide
      Potassium iodide
      Potassium hypochlorite
      Potassium chlorate
      Potassium perchlorate
      Potassium hypobromite
      Potassium bromate
      Potassium perbromate
      Potassium hypoiodite
      Potassium iodate
      Potassium periodate
      Potassium monoxide
      Potassium peroxides
      Potassium hydroxide
      Potassium monosulphide
      Potassium sulphide
      Potassium polysulphides
      Potassium hydrogen sulphide
      Potassium sulphite
      Potassium hydrogen sulphite
      Potassium pyrosulphite
      Potassium sulphate
      Potassium hydrogen sulphate
      Potassium pyrosulphate
      Potassium persulphate
      Potassium thiosulphate
      Potassium dithionate
      Potassium trithionate
      Potassium tetrathionate
      Potassium pentathionate
      Potassium hyposulphite
      Potassium selenides
      Potassium selenate
      Potassium tellurides
      Potassium tellurate
      Potassium nitride
      Potassium hydrazoate
      Potassamide
      Potassium hyponitrite
      Potassium nitrite
      Potassium nitrate
      Potassium phosphides
      Potassium hypophosphite
      Potassium orthophosphates
      Potassium pyrophosphate
      Potassium metaphosphate
      Potassium arsenite
      Potassium arsenates
      Potassium carbide
      Potassium carbonate
      Potassium sodium carbonate
      Potassium bicarbonate
      Potassium hydrogen carbonate
      Potassium percarbonate
      Potassium thiocarbonate
      Potassium cyanide
      Potassium thiocyanate
      Potassium silicates
      Potassium fluosilicate
      Potassium silicofluoride
      Potassium hypoborate
      Potassium borates
      Dipotassium tetraborate
      Potassium perborates
      Potassium oxalate
    PDB 1a3w-1dul
    PDB 1dz4-1j95
    PDB 1jbr-1lqp
    PDB 1lrt-1o07
    PDB 1o76-1qb9
    PDB 1qj5-1t86
    PDB 1t87-1vq9
    PDB 1vqk-1yj9
    PDB 1yjn-2aop
    PDB 2apo-2f4v
    PDB 2fbw-2hg9
    PDB 2hh1-2oij
    PDB 2oiy-2uxb
    PDB 2uxc-2x20
    PDB 2x21-3c0y
    PDB 3c0z-3dix
    PDB 3diy-3f5w
    PDB 3f7j-3hqo
    PDB 3hqp-3l01
    PDB 3l0u-3oi5
    PDB 3oia-3r9b
    PDB 3rde-4e6k
    PDB 4edj-8gep

Potassium perchlorate, KClO4






Careful heating of potassium chlorate causes partial autoxidation to Potassium perchlorate, KClO4:

4KClO3 = 3KClO4 + KCl.

The slight solubility of the perchlorate in dilute alcohol affords a means of separating it from the chloride. According to Blau and Weingland, the decomposition of the chlorate is best carried out in quartz flasks at 480° C. without a catalyst, but when between 96 and 97 per cent, of the chlorate has been transformed the perchlorate begins to decompose, so that the change is never complete. The decomposition of the perchlorate is much accelerated by the presence of traces of iron oxide, copper, nickel, boron trioxide, or potassium hydroxide, so that vessels made of iron are unsuitable for its preparation.

When sulphuric acid reacts with potassium chlorate without application of heat, a yield of 11 per cent, of the perchlorate is obtained. Boiling with phosphoric acid of 85 per cent, strength gives a 15 per cent, yield; and evaporation to dryness with nitric acid produces a 30 per cent, yield. Hydrochloric acid does not form any perchlorate.

A good yield of the perchlorate is obtained by the electrolysis of potassium chlorate with a platinum anode and a nickel cathode, the current density being 0.15 ampere per square decimetre. Even when revolving rapidly, the electrodes become incrusted with perchlorate; but this difficulty may be avoided by electrolyzing sodium chlorate, and forming potassium perchlorate by double decomposition. Knibbs and Palfreeman regard the electrolytic formation of perchlorate as being analogous to that of persulphate, and give the scheme

-O2ClO- + -OClO2 = [O2ClO-]2;
[O2ClO-]2 + H2O = O2ClO-OH + O2ClOH.

The salt forms colourless, rhombic crystals, melting at 610° C. Its density is given as 2.524 at 10.8° C., and 2.520 at ordinary temperature. The specific heat is 0.190 between 14° and 45° C. The heat of formation from the elements is 112.5 Cal. The solubility at 25° C. is 1.96 grams per 100 grams of water. Above 400° C. the salt decomposes with evolution of oxygen and formation of KCl. Its insolubility in alcohol renders it of service in the estimation of potassium.


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