Sieverts' law

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Sieverts' law, in physical metallurgy and in chemistry, is a rule to predict the solubility of gases in metals. It is named after German chemist Adolf Sieverts (1874–1947).[1] The law states that the solubility of a diatomic gas in metal is proportional to the square root of the partial pressure of the gas in thermodynamic equilibrium.[2] Hydrogen, oxygen and nitrogen are examples of dissolved diatomic gases of frequent interest in metallurgy.

Justification[edit]

Sieverts' law can be readily rationalized by considering the reaction of dissolution of the gas in the metal, which involves dissociation of the molecule of the gas. For example, for nitrogen:

N2 (molecular gas) ⇌ 2 N (dissolved atoms)

For the above reaction, the equilibrium constant, K, is:

Where:

  • cat is the concentration of the dissolved atoms into the metal (in the case above atomic nitrogen N)
  • pmol is the partial pressure of the gas at the interface with the metal (in the case above, the molecular nitrogen N2)

Therefore,

See also[edit]

References[edit]

  1. ^ Sieverts, Adolf (1929). "The Absorption of Gases by Metals". Zeitschrift für Metallkunde. 21: 37–46. 
  2. ^ C. K. Gupta, "Chemical metallurgy: principles and practice", Wiley-VCH, 2003, p.273.