0.1 N Ceric Sulfate Solution Preparation & Standardization

0.1 N Ceric Sulfate Solution

 Preparation of  0.1 N Ceric Sulfate Solution                                  

Warning-1 —The addition of water to the sulfuric acid slurry in this procedure should be carried out slowly and cautiously, as the resulting solution becomes very hot and may
spatter. Wear a face-shield during the operation. 

• 60 g of ceric ammonium nitrate [(NH4)2·Ce(NO3)6]
• Add 30 mL of concentrated sulfuric acid (H2SO4 sp gr 1.84),and stir until a smooth slurry is formed. 
• Add, cautiously and with constant stirring, 100 mL of water (Warning See 1)  and stir for 2 min when addition is complete. 
• Add 600 mL of additional water in three portions, adding the water slowly, and stirring for 2 min after each 200 mL is added. 
• Dilute with water to 900 mL, cool, filter through a glass microfiber filter, and let the filtrate stand undisturbed in a tightly-closed glass container for 2 or 3 days.
• If the solution is clear after standing, dilute it with water to 1 L. Store the solution in tightly-closed glass containers.
• If any insoluble matter precipitates during the standing, filter as above and dilute the filtrate with water to 1 L.

Standardization  of  0.1 N Ceric Sulfate Solution                                  

• Transfer about 1 g of primary standard arsenic triox-ide (As2O3) to a platinum dish, and dry at 105°C for 1 h. Cool in a desiccator. 
• Weigh accurately 0.20 ± 0.01 g of the dried As2O3 and transfer to a 500-ml conical flask. 
• Rinse the walls of the flask with 25 mL of water containing 2 g of sodium hydroxide (NaOH), and swirl to dissolve. When solution is complete, dilute with 100 mL of water, 
• Add 10 mL of sulfuric acid (H2SO4, 1 + 1), 3 drops of a solution of 0.01 M osmium tetroxide (OsO4) (Warning, see 2) in 0.1 N H2SO4 , and 
• 2 drops of 0.025 M, 1,10-phenanthroline ferrous sulfate indicator solution. 
• Titrate slowly with the ceric sulfate solution to the sharp color change from pink to very pale blue.

 Calculation                             

Calculate the normality of the ceric sulfate solution, as follows:
       A = B / 0.04946 3 * C