688.5 g/kg = 691.874 PSU
| g/kg | PSU |
|---|---|
| 673.5 g/kg | 676.8 |
| 678.5 g/kg | 681.825 |
| 683.5 g/kg | 686.849 |
| 688.5 | 691.874 |
| 693.5 g/kg | 696.898 |
| 698.5 g/kg | 701.923 |
| 703.5 g/kg | 706.947 |
688.5 g/kg = 691.874 PSU
1 g/kg ≈ 1.0049 PSU · 1 mg/L ≈ 0.001 PSU · 1 ppm ≈ 0.001 PSU (dilute aqueous approximation)