Diphenylamine Sulfonate for the Determination of Iron with K2Cr2O7

The diphenylamine sulfonate for the titration of iron using potassium dichromate (K2Cr2O7). This method is effective in determining iron concentrations, and the addition of diphenylamine sulfonate increases the accuracy of the analysis.

Titration is a method used in analytical chemistry to accurately determine the concentration of a particular substance. 

6 Fe^2+ + Cr2O7^2- + 14 H+ → 6 Fe^3+ + 2 Cr^3+ + 7 H2O


Take accurat weight 0.32 g of the barium salt of diphenylamine sulfonic acid with the help of an analytical balance.

Dissolve the weighted diphenylamine sulfonate (BA salt) in 100 ml of distilled water. Shake and mix the solution gently to ensure complete dissolution.

Now add 0.5 g of sodium sulfate (Na2SO4) to the diphenylamine sulphonate solution and mix well. Sodium sulfate helps prevent the precipitation of unwanted impurities during titration.

Diphenylamine Sulfonate for the Determination of Iron with K2Cr2O7

Filter the resulting solution to remove any insoluble impurities or precipitate of barium sulfate (BaSO4).

There is a clear filtrate in a clean container, which is to be used as the titration solution.

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Prepare a standardized solution of potassium dichromate (K2Cr2O7) by dissolving a known mass of the compound in distilled water. Whose concentration should be known.

Take a sample containing iron ions in a conical flask.

A few drops of diphenylamine sulphonate solution are added to the flask. And diphenylamine sulfonate reacts with iron(II) ions (Fe2+) to form a blue-colored complex.

Slowly add (titration with) standardized potassium dichromate solution to the flask, and mix it until the blue color of the complex disappears completely.

Note down the amount of potassium dichromate solution consumed during the titration.

Repeat the titration process at least three times to ensure the accuracy and consistency of the results.

Calculate the concentration of iron in the sample using the volume of potassium dichromate solution consumed and the known concentration of K2Cr2O7 solution.

Calculation Formula

Concentration of Iron (in moles/L) = (Volume of K2Cr2O7 solution consumed in Liters) * (Molarity of K2Cr2O7 solution) * (Moles of Iron per Mole of K2Cr2O7),


This titration method using diphenylamine sulfonate and potassium dichromate is a reliable method of determining the concentration of iron in a sample. By directly following the calculation formula, it can measure the iron content accurately. This method's simplicity and effectiveness make it valuable for a variety of analytical applications in research, industries, and laboratories.

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Note: Always give priority to safety while working with chemicals in the laboratory. Read appropriate references, such as lab manuals and safety data, for detailed instructions and precautions before performing any experiments.


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