solvophobicity parameter, Sp

$Sp = 1 − M M hexadecane$

derived from the Gibbs energy of transfer ( $Δ t G °$ ) of a series of solutes from water to numerous aqueous-organic mixtures and to pure solvents:

$Δ t G ° to solvent = M R T + D$

where $R T$ is a solute parameter, and $M$ and $D$ characterize the solvent. The $M$ values are used to define a solvent solvophobic effect so that $S p$ values are scaled from unity (water) to zero (hexadecane).

Source:

PAC, 1994, 66, 1077 (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1165