Hach POCKET COLORIMETER II Instruction Manual page 23

10.
Subtract the reagent
blank from the reading for
true concentration.
Phosphorus, Reactive,
To convert reading
from
mg/L PO
mg/L PO
To convert results to other units, use conversion
Note:
1—23
Table 2
To
mg/L P O
3–
2
4
mg/L P
3–
4
continued
Multiply by
0.747
5
0.326
Table 2 .