690.5 PSU = 687.133 g/kg
| PSU | g/kg |
|---|---|
| 675.5 PSU | 672.2062 |
| 680.5 PSU | 677.1818 |
| 685.5 PSU | 682.1574 |
| 690.5 PSU | 687.133 |
| 695.5 PSU | 692.1087 |
| 700.5 PSU | 697.0843 |
| 705.5 PSU | 702.0599 |
690.5 PSU = 687.133 g/kg
1 g/kg ≈ 1.0049 PSU · 1 mg/L ≈ 0.001 PSU · 1 ppm ≈ 0.001 PSU (dilute aqueous approximation)