684.5 g/kg = 687.854 PSU
| g/kg | PSU |
|---|---|
| 669.5 g/kg | 672.781 |
| 674.5 g/kg | 677.805 |
| 679.5 g/kg | 682.83 |
| 684.5 | 687.854 |
| 689.5 g/kg | 692.879 |
| 694.5 g/kg | 697.903 |
| 699.5 g/kg | 702.928 |
684.5 g/kg = 687.854 PSU
1 g/kg ≈ 1.0049 PSU · 1 mg/L ≈ 0.001 PSU · 1 ppm ≈ 0.001 PSU (dilute aqueous approximation)