## 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 @M04000@, the value of the @S05740-1@ parameter can be estimated most reliably from the @E02141@ of vaporization and the molar volume.
2. The @S05740-1@ of a substance B can be related to the square of the difference between the @S05740-1@ parameters for supercooled liquid B and solvent at a given temperature, with appropriate allowances for @E02149@ of mixing. Thus, a value can be estimated from the @S05740-1@ of the solid in a series of solvents of known @S05740@ parameter. For a polymer, it is usually taken to be the value of the @S05740-1@ parameter of the solvent producing the solution with maximum intrinsic @V06627@ or maximum swelling of a @NT07562@ of the polymer. See J.H. Hildebrand, R.L.Scott, The @S05740-2@ 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 $$\text{Pa}^{1/2} = \text{J}^{1/2}\ \text{m}^{-3/2}$$, but units used frequently are $$(\unicode[times]{x3BC}\text{Pa})^{1/2} = (\text{J cm}^{-3})^{1/2}$$ or $$(\text{cal cm}^{-3})^{1/2}$$, where $$1\ (\text{J cm}^{-3})^{1/2} \approx 2.045(\text{cal cm}^{-3})^{1/2}$$. The unit @C00784@ 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.