666.5 PSU = 663.2501 g/kg
| PSU | g/kg |
|---|---|
| 651.5 PSU | 648.3232 |
| 656.5 PSU | 653.2988 |
| 661.5 PSU | 658.2745 |
| 666.5 PSU | 663.2501 |
| 671.5 PSU | 668.2257 |
| 676.5 PSU | 673.2013 |
| 681.5 PSU | 678.1769 |
666.5 PSU = 663.2501 g/kg
1 g/kg ≈ 1.0049 PSU · 1 mg/L ≈ 0.001 PSU · 1 ppm ≈ 0.001 PSU (dilute aqueous approximation)