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COD from Blank and Sample Titrations

Calculate an uncorrected titrimetric chemical oxygen demand from blank/sample FAS volumes, normality and sample aliquot volume.

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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

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Formula and method

Blank titration 10 mL, sample titration 8 mL, titrant 0.1 eq/L and sample aliquot 20 mL give uncorrected COD 80 mg O₂/L.

COD in mg O₂/L = (blank mL − sample mL) × FAS eq/L × 8000 / sample aliquot mL

Worked example

Enter these known values and leave the other values blank.

FAS titrant used for the blank
10 mL
FAS titrant used for the sample
8 mL
Standardized FAS equivalent concentration
0.1 eq/L
Analyzed sample aliquot volume
20 mL
Uncorrected oxygen-equivalent demand
80 mg/L

Assumptions and limitations

  • Titrant and aliquot volumes and titrant concentration are positive; the blank volume must be at least the sample titration volume for a nonnegative result.
  • This is the basic arithmetic for a suitable dichromate/FAS titration, using 8000 mg oxygen per equivalent. It does not validate laboratory preparation, endpoints or titrant standardization.
  • Dilution factors and interference corrections are not included. For example, the cited saline-water method requires a chloride correction beyond this uncorrected result.

Common questions

Is the result dissolved oxygen concentration?

No. COD expresses an oxygen-equivalent demand inferred from the oxidation test; it is not a measurement of oxygen dissolved in the sample.

Does this certify a result under the cited method?

No. The tool calculates the uncorrected titration balance only. Method-specific corrections, quality controls and sample handling remain separate.

References

The calculation equations, inverse formulas, units, and input rules were imported from this source. Bookify provides the interface and equation solver.

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