## solubility parameter, $$\delta$$

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, $\delta _{\text{B}} = \left ( \frac{\Delta _{\text{vap}}E_{\text{m,B}}}{V_{\text{m,B}}} \right )^{1/2}$ where Δvap.Em,B is the molar energy of vaporization at zero pressure and Vm,B is the molar volume.
Notes:
1. For a substance of low @[email protected], the value of the @[email protected] parameter can be estimated most reliably from the @[email protected] of vaporization and the molar volume.
2. The @[email protected] of a substance B can be related to the square of the difference between the @[email protected] parameters for supercooled liquid B and solvent at a given temperature, with appropriate allowances for @[email protected] of mixing. Thus, a value can be estimated from the @[email protected] of the solid in a series of solvents of known @[email protected] parameter. For a polymer, it is usually taken to be the value of the @[email protected] parameter of the solvent producing the solution with maximum intrinsic @[email protected] or maximum swelling of a @[email protected] of the polymer. See J.H. Hildebrand, R.L.Scott, The @[email protected] 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). The unit @[email protected] is discouraged as obsolete.
Source:
PAC, 2008, 80, 233. 'Glossary of terms related to solubility (IUPAC Recommendations 2008)' on page 264 (https://doi.org/10.1351/pac200880020233)
This definition replaces an earlier definition of solubility parameter, δ.