685.5 g/kg = 688.859 PSU
| g/kg | PSU |
|---|---|
| 670.5 g/kg | 673.785 |
| 675.5 g/kg | 678.81 |
| 680.5 g/kg | 683.834 |
| 685.5 | 688.859 |
| 690.5 g/kg | 693.883 |
| 695.5 g/kg | 698.908 |
| 700.5 g/kg | 703.932 |
685.5 g/kg = 688.859 PSU
1 g/kg ≈ 1.0049 PSU · 1 mg/L ≈ 0.001 PSU · 1 ppm ≈ 0.001 PSU (dilute aqueous approximation)