Chemical elements
  Potassium
    Isotopes
    Energy
    Preparation
    Physical Properties
      Potassium Ion
      Weight of Potassium
      Alloys
    Chemical Properties
    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

Physical Properties of Potassium






Potassium is a soft, silver-white metal of high lustre. Its melting-point is given as 60° C., 62.4° C., 62.5° C., and 63.5° C. A wide discrepancy exists between the values given for the boiling-point, among them being 667° C.; 667° C. at 760 mm. pressure, 719° to 731° C., 757.5° C., 365° C. at 0 mm., and about 90° C. in the vacuum of the cathode light. For the density are recorded the values 0.8629 and 0.859 at 0° C., 0.8621 at 20° C., and 0.851 (solid) and 0.8298 (liquid) at 62.1° C. The atomic volume calculated from the value at 20° C. is 45.35. The metal has a lower density and a higher atomic volume than sodium.

At ordinary temperature potassium has a wax-like consistence, its hardness being 0.5, the corresponding values for the other alkali-metals being lithium 0.6, sodium 0.4, rubidium 0.3, and caesium 0.2. At low temperatures the metal becomes hard and brittle. Like sodium, it crystallizes in cubes and also in quadratic octahedra. In reflected light it has a greenish-blue colour, that of light transmitted through very thin layers being violet-blue. At the boiling-point its vapour is green, at bright redness violet.

Between -78.5° and 23° C. the specific heat is given as 0.1662, corresponding with the atomic heat 6-5. The specific heat increases rapidly with rise in temperature, the value recorded between 22.3° and 56.5° C. being 0.1922. For the specific heat of the solid at the melting-point, Rengade gives 0.1914. The latent heat of fusion has been found by Joannis to be 15.7 Cal. per kilogram, and by Rengade to be 14.63 Cal. The metal is a good conductor of heat and electricity, and displays slight magnetic properties. The "velocity of sound" method indicates the monatomicity of potassium vapour.

Potassium and many of its salts are said to exhibit radioactivity, the amount of radium present in a gram of the chloride, sulphate, carbonate, or nitrate being given as 3×10-14. Some authorities deny the existence of radioactive properties.


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