Analysis of Iron in Preflux and Pickling Acid tanks using the dropper bottle method

1.0   Purpose

1.1   To provide quick, reliable in house test results.

2.0   Reagents

2.1   IRON TITRANT:  Potassium Dichromate (K₂Cr₂O₇ M.W. 294.19).  This solution is used dropwise to determine the amount of iron in the sample.  This yellow solution is toxic.  Make sure to flush with water when it comes in contact with skin.  Read MSDS sheet

2.2   IRON BUFFER:  This solution is a mixture of Sulfuric acid and Phosphoric acid and is very corrosive. Make sure to flush with water when it comes in contact with skin.  Read MSDS sheet

2.3   IRON INDICATOR:  Clear solution needed to determine color change when using titrant.

3.0   PROCEDURE

3.1   Use 0.5 ml (cc) sample for acid or  use 5 ml (cc) sample for preflux or 1 ml (cc)  sample for rinse tanks.  Using the syringes provided add the appropriate size sample  to 25 ml distilled water in the 50 ml flask.

3.2   Add 2 ml Iron buffer to the solution.

3.3   Add 4 drops of Iron indicator to solution and swirl to mix.

3.4   Titrate with Iron Titrant Potassium Dichromate (K₂Cr₂O₇)  to blue end point making sure to count the drops of titrant needed to change the color to blue.  Swirl solution after each drop.

4.0   CALCULATIONS  (Specific gravity of acid assumed 1.30 g/ml)

4.1   For a 0.5 ml sample each drop is equal to 0.5 % wt. iron or 5000 ppm.

4.2   For a 1.0 ml sample each drop is equal to 0.25 % wt. iron or 2500 ppm.

4.3   For a 5.0 ml sample each drop is equal to 0.05 % wt. iron or 500 ppm.