|δd||the dispersion contribution to δ|
|δp||the polar contribution to δ|
|δh||the hydrogen bonding contribution to δ|
The relation δ2=δd2+δp2+δh2 holds. Thus for non-polar solvents δp=δh=0 and δd=δ.
Solutes do also have δd,δp and δh parameters and an additional parameter, the interaction radius, R0. To determine the solubility of a compound the distance Ra is calculated.
|Ra2= 4×Δδd2+ Δδp2+ Δδh2|
For a more detailed discussion see →The Official Hansen Solubility Parameter Site or →Solubility Parameters: Theory and Application
The parameters here are given in (cal/ml)½. To convert to MPa½ multiply by 2.05.