639.5 mg/L = 639.5 ppm
| mg/L | ppm |
|---|---|
| 624.5 mg/L | 624.5 |
| 629.5 mg/L | 629.5 |
| 634.5 mg/L | 634.5 |
| 639.5 | 639.5 |
| 644.5 mg/L | 644.5 |
| 649.5 mg/L | 649.5 |
| 654.5 mg/L | 654.5 |
639.5 mg/L = 639.5 ppm
1 ppm = 1 mg/L (aqueous, density ≈ 1 kg/L) · 1 ppb = 0.001 mg/L · 1% = 10,000 ppm