This command has not yet been ported to the new APBS syntax (see new_input_format).
Specify the monovalent salt concentration of the system, in molar. This is usually a value between 0.00 to 0.15.
salt {saltConc}where saltConc is the floating point value of the monovalent salt concentration in molar.
The PB-(S)AM salt keyword should be eradicated and replaced with the ion keyword. Documented in https://github.com/Electrostatics/apbs/issues/501