684.5 PSU = 681.1623 g/kg
| PSU | g/kg |
|---|---|
| 669.5 PSU | 666.2354 |
| 674.5 PSU | 671.2111 |
| 679.5 PSU | 676.1867 |
| 684.5 PSU | 681.1623 |
| 689.5 PSU | 686.1379 |
| 694.5 PSU | 691.1135 |
| 699.5 PSU | 696.0892 |
684.5 PSU = 681.1623 g/kg
1 g/kg ≈ 1.0049 PSU · 1 mg/L ≈ 0.001 PSU · 1 ppm ≈ 0.001 PSU (dilute aqueous approximation)