643.5 g/kg = 646.653 PSU
| g/kg | PSU |
|---|---|
| 628.5 g/kg | 631.58 |
| 633.5 g/kg | 636.604 |
| 638.5 g/kg | 641.629 |
| 643.5 | 646.653 |
| 648.5 g/kg | 651.678 |
| 653.5 g/kg | 656.702 |
| 658.5 g/kg | 661.727 |
643.5 g/kg = 646.653 PSU
1 g/kg ≈ 1.0049 PSU · 1 mg/L ≈ 0.001 PSU · 1 ppm ≈ 0.001 PSU (dilute aqueous approximation)