Yes, salinity can be calculated from the chloride ion concentration using Go Direct® Chloride Ion-Selective Electrode (GDX-CL) or Chloride Ion-Selective Electrode (CL-BTA) using the following equation:
salinity (ppt) = 0.0018066 x Cl– (mg/L)*
This equation is only valid for ocean water, not fresh or brackish water.
The complete procedure can be found in Water Quality with Vernier (WQV).
*Woolsey, et al, 1969