solubility parameter, δ

https://doi.org/10.1351/goldbook.ST07466
Parameter used in predicting the solubility of non-electrolytes (including polymers) in a given solvent.
For a substance B, δB=(ΔvapEm,BVm,B)1/2 where ΔvapEm,B is the molar energy of vaporization at zero pressure and Vm,B is the molar volume.
Notes:
  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 Pa1/2=J1/2 m−3/2, but units used frequently are (μPa)1/2=(Jcm−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.
Source:
PAC, 2008, 80, 233. (Glossary of terms related to solubility (IUPAC Recommendations 2008)) on page 264 [Terms] [Paper]
This definition replaces an earlier definition of solubility parameter, δ.
Citation: 'solubility parameter' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.ST07466 RIS BibTex EndNote
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