Prepare 0.1 mol/l Ferric Ammonium Sulfate Solution

General Information:

       One liter of this solution contains 48.22 g of ferric ammonium sulfate (Fe(NH4) (SO4)ŋ12H2O, molecular weight: 482.19).

Procedure:
      Weigh 49 g of ferric ammonium sulfate, dissolve in cooled mixture of ̒ml of sulfuric acid and  300 ml of water, and add water to make 1,000 ml.
 

Standardization: 

       Measure exactly 25 ml of 0.1 mol/l ferric ammonium sulfate into an iodine-flask, add 5 ml of hydrochloric acid and shake. Add and dissolve 2 g of potassium iodide, stopper tightly, and allow to stand for 10 minutes. Add 50 ml of water, titrate liberated iodine with 0.1 mol/l sodium thiosulfate. When the color of the solution changes to light yellow near the end point, add 3 ml of starch TS as the indicator, and continue the titration until the blue color of the solution disappears. Perform a blank test in the same manner, and make any necessary correction. Store, protecting from light, and restandardize frequently.