642.5 g/kg = 645.648 PSU
| g/kg | PSU |
|---|---|
| 627.5 g/kg | 630.575 |
| 632.5 g/kg | 635.599 |
| 637.5 g/kg | 640.624 |
| 642.5 | 645.648 |
| 647.5 g/kg | 650.673 |
| 652.5 g/kg | 655.697 |
| 657.5 g/kg | 660.722 |
642.5 g/kg = 645.648 PSU
1 g/kg ≈ 1.0049 PSU · 1 mg/L ≈ 0.001 PSU · 1 ppm ≈ 0.001 PSU (dilute aqueous approximation)