Chemical elements
    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
      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 carbonate, K2CO3

The Potassium carbonate, K2CO3 is a constituent of the ashes of wood and other vegetable products, and is obtained by extracting with water, the purified product being known as "pearl-ash." The origin of the world " potash " has occasioned some controversy. It has been attributed by some to the name of the chemist Pott (1692-1777), but it appears to have been in use before his birth. Three other explanations have been advanced: the use of pots, and later boilers, in the concentration of the aqueous extract of the crude ashes; the employment of pots in the incineration of the wood; and the fact that ashes collected under the cooking-pots on the hearth fires of the Middle Ages. The first of these three explanations seems to be the most plausible.

Modern manufacturing methods depend on the conversion of potassium chloride into carbonate by electrolysis; by the Le Blanc process; or by the action of magnesium carbonate, carbon dioxide, and water:

3MgCO3 + 2KCl + CO2 + H2O = 2MgKH(CO3)2 + MgCl2.

The precipitated double carbonate is decomposed by hot water:

2MgKH(CO3)2 = 2MgCO3 + K2CO3 + CO2 + H2O.

Potassium carbonate is also manufactured from the spent wash of the spirit-distiller, and from the residual liquor of the wool-scourer.

Potassium carbonate is a white solid. Its melting-point is given by various experimenters as 878.6° C., 880° C., 885° C., 873.1° C., 887.5° C., 891° C., 894° C., 897.3° C., 897.7° C., 900° C. For the density the mean value is given as 2.29; a more recent determination gives 2.3312 at 17° C. Its specific heat is 0.206 between 17° and 47° C., and 0.2162 between 23° and 99° C. At 970° C. the vapour-pressure is 1.68 mm.; and at 1130° C. it is 5.0 mm. The heat of formation from the elements is recorded as 275.37 Cal., 278.8 Cal., and 281.1 Cal. Potassium carbonate exhibits diamagnetism.

Several hydrates have been described, but their constitutions are not definitely settled. At 25° c. the solubility is 113.5 grams per 100 grams of water, and at 130° c. it is 196 grams. The aqueous solution has a strong alkaline reaction, due to hydrolytic dissociation. It forms various primary carbonates by interaction with atmospheric carbon dioxide, and unites with hydrogen peroxide yielding compounds of the formulae K2CO3,3H2O2 and K2CO3,2H2O2H2O.

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