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solubility parameter, δ

Parameter used in predicting the solubility of non-electrolytes (including polymers) in a given solvent.
For a substance B,
δ B = ( Δ vap E m , B V m , B ) 1/2
where Δ vap E m , B is the molar energy of vaporization at zero pressure and V m , B is the molar volume.
  1. For a substance of low molecular weight, the value of the solubility parameter can be estimated most reliably from the enthalpy of vaporization and the molar volume.
  2. The solubility of a substance B can be related to the square of the difference between the solubility parameters for supercooled liquid B and solvent at a given temperature, with appropriate allowances for entropy of mixing. Thus, a value can be estimated from the solubility of the solid in a series of solvents of known solubility parameter. For a polymer, it is usually taken to be the value of the solubility parameter of the solvent producing the solution with maximum intrinsic viscosity or maximum swelling of a network of the polymer. See J.H. Hildebrand, R.L.Scott, The Solubility of Nonelectrolytes, 3rd ed., Reinhold Publishing (1950); Dover Publications (1964), Chap. VII, p.129; Chap. XXIII, for the original definition, theory, and extensive examples.
  3. The SI units are Pa 1/2 = J 1/2 m −3/2, but units used frequently are µPa 1/2 = ( J cm −3 ) 1/2 or ( cal cm −3 ) 1/2, where 1 ( J cm −3 ) 1/2 ≈ 2.045 ( cal cm −3 ) 1/2. The unit calorie is discouraged as obsolete.
PAC, 2008, 80, 233 (Glossary of terms related to solubility (IUPAC Recommendations 2008)) on page 264
This definition replaces an earlier definition of solubility parameter, δ.
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IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). XML on-line corrected version: (2006-) created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8.
Last update: 2014-02-24; version: 2.3.3.
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