Chemical Oxygen Demand (COD) Calculator

What is Chemical Oxygen Demand (COD)?

Chemical Oxygen Demand (COD) is a measure of the amount of oxygen that can be consumed by reactions in a measured solution. It is used as an indicator of the organic pollutants in water.

How to Use the Calculator

1. Volume of Sample (V_sample, mL): Enter the volume of your water sample into the calculator.

Example: 50 mL

2. Volume of Titrant (V_titrant, mL): Input the volume of titrant used during titration.

Example: 5 mL

3. Normality of Titrant (N_titrant, N): Enter the normality of the titrant.

Example: 0.1 N

4. Volume of Blank (V_blank, mL): Input the volume of the blank sample used.

Example: 0.0 mL

5. Dilution Factor (D): Enter the dilution factor of your sample.

Example Inputs

• Volume of Sample: 50 mL
• Volume of Titrant: 5 mL
• Normality of Titrant: 0.1 N
• Volume of Blank: 0.0 mL
• Dilution Factor: 1

When you fill in these values and click “Calculate,” the calculator will compute the COD.

Formula

The formula to calculate the Chemical Oxygen Demand (COD) is:

$\text{COD}=\frac{(V_{blank}-V_{titrant})\times N_{titrant}\times 8000}{V_{sample}}$

Variable	Description
$\text{COD}$	Chemical Oxygen Demand (mg/L)
$V_{blank}$	Volume of Blank (mL)
$V_{titrant}$	Volume of Titrant (mL)
$N_{titrant}$	Normality of Titrant (N)
$V_{sample}$	Volume of Sample (mL)
$D$	Dilution Factor

Calculation Examples

Example 1

• Volume of Sample (V_sample): 50 mL
• Volume of Titrant (V_titrant): 5 mL
• Normality of Titrant (N_titrant): 0.1 N
• Volume of Blank (V_blank): 0.0 mL
• Dilution Factor (D): 1

Calculation:

1.  Plug the values into the formula:

$\text{COD}=\frac{(0.0-5)\times 0.1\times 8000}{50}$

2. Calculate the numerator:

$(0.0-5)\times 0.1\times 8000=-5\times 0.1\times 8000=-4000$

3. Divide the numerator by the volume of the sample:

$\frac{-4000}{50}=-80$

4. The COD is:

$\text{COD}=-80\text{ mg/L}$

Example 2

• Volume of Sample (V_sample): 100 mL
• Volume of Titrant (V_titrant): 10 mL
• Normality of Titrant (N_titrant): 0.2 N
• Volume of Blank (V_blank): 2.0 mL
• Dilution Factor (D): 1

Calculation:

Plug the values into the formula:

$\text{COD}=\frac{(2.0-10)\times 0.2\times 8000}{100}$

2. Calculate the numerator:

$(2.0-10)\times 0.2\times 8000=-8\times 0.2\times 8000=-12800$

3. Divide the numerator by the volume of the sample:

$\frac{-12800}{100}=-128$

4. The COD is:

$\text{COD}=-128\text{ mg/L}$