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 nitrate, KNO3






The Potassium nitrate, KNO3 is manufactured from natural saltpetre earths found in Bengal, and to a less extent in Egypt and elsewhere. The nitrate in these earths is produced by the oxidation of organic matter by the action of " nitrifying " bacteria in presence of atmospheric oxygen, a warm, moist climate being particularly favourable for the process. The nitrate is extracted by lixiviating the earth in vessels of earthenware or wood, and concentrating the aqueous solution in iron pots by solar or artificial heat.

Artificial saltpetre earths can be prepared by allowing stable refuse to nitrify in contact with a porous soil containing calcium carbonate, the nitrate being isolated by lixiviation and purified by crystallization. The salt is also manufactured from sodium nitrate by the action of potassium chloride, since it crystallizes out from a hot concentrated solution of these two substances as the temperature falls. When prepared from Chile saltpetre, it often contains sodium nitrate, and chloride, chlorate, and perchlorate of potassium.

The extraordinary demand for nitric acid and nitrates brought about by the abnormal conditions consequent on the great European War of 1914 and succeeding years gave a powerful impetus to the development of synthetic methods for the fixation of atmospheric nitrogen.

At ordinary temperature, potassium nitrate crystallizes in the rhombic system, at higher temperatures the crystals formed are rhombohedral. The transition-point is 129.5° C. The second form is said to exist in two modifications, α and β. - Among the values given for the melting-point are 333° C., 334.5° C., and 339° C.; for that of the rhombohedral form 334° C. For the density the mean value is given as 2.092, other determinations giving 2.1047, 2.109 at 16° C., 2.109 at 20° C., and 2.044-0.0006t at temperatures ranging from 350° to 500° C. The heat of formation from the elements is given as 119 Cal. And 119.5 Cal. The molecular electric conductivity of potassium nitrate between 346.1° and 500.4° C. is given by the formula

μt = 36.21 + 0.1875(t-350).

Potassium nitrate does not form hydrates. Its solubility in water increases rapidly with rise of temperature, as indicated by the table:

Solubility of Potassium Nitrate.

Temperature, °C0102030405060708090100110120125
Grams KNO3 in 100g. of water.13.320.931.645.863.985.5110.0138169202246300394493


The boiling-point of a solution in contact with excess of salt is 115.55° C. at 760 mm. pressure. The salt exhibits triboluminescence, and is diamagnetic.

On heating, potassium nitrate is converted into the nitrite, with evolution of oxygen. It finds application as an oxidizer, notably in the detonation of gunpowder, the cheaper sodium nitrate being inadmissible on account of its hygroscopic nature. The usual composition of this explosive is 75 per cent, of potassium nitrate, 15 per cent, of carbon, and 10 per cent, of sulphur. In contact with the fused nitrate, carbon and sulphur become ignited, and burn with evolution of the corresponding dioxide and nitrogen, and formation of other products. In dilute solution the nitrate is partially transformed by the action of ultraviolet rays into potassium nitrite and oxygen.

KNO3,2HNO3 with water
Behaviour of KNO3,2HNO3 with water
Two acid potassium nitrates have been isolated: a dinitrate, KNO3,HNO3, stable at 22° to 28° C., and a trinitrate, KNO3,2HNO3, melting at 22° C. The behaviour of the trinitrate with water is graphically represented in Fig.


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