Preparation of prussian blue, fe4[fe(cn)6]3

Prussian blue is having many applications in the pharmaceutical and paint industries

1. Preparation of Prussian Blue, Fe 4 [Fe(CN) 6 ] 3 By Dr Bhavana P Khobragade RDIK and NKD College Badnera

2. Prussian Blue

3. Theory The complex iron hexacyano ferrate is known as prussian blue It is obtained by oxidation of iron , Fe to Fe 3+ , followed by reaction with potassium ferrocyanide . Fe + H 2 SO 4 → FeSO 4 + H 2 2FeSO 4 + H2SO 4 +[0]→ Fe 2 (SO4) 3 +H 2 Fe 2 (SO 4 ) 3 + 2K 2 [Fe(CN) 6 ] 3 → Fe 4 [Fe(CN) 6 ] 3 + 5K 2 SO 4 Fe → Fe 4 [Fe(CN) 6 ) 3 MW = 55.85 g MW = 859.25 g

4. Apparatus : 100 ml beaker, measuring cylinders, etc.

5. Chemicals Iron filings, potassium ferrocyanide , dil.Sulfuric Acid , Conc . HNO 3 , ethanol, etc.

6. Procedure Take 0.5 g of iron filings in a beaker. Add 10 ml of dil. sulfuric acid. Heat it on a wire guaze . The reaction becomes vigorous Remove the burner and cool the solution. When the reaction subsides, decant the supernatant liquid in another beaker. Add 10 ml of dil. sulfuric acid Repeat the procedure till whole iron filings are dissolved. Combine the solution of ferrous sulfate and heat it. Add 0.5 ml conc. HNO 3 and boil to oxidize iron to ferric state. The solution becomes yellow. Continue boiling for 5 minutes to expel fumes of NO 2 gas and nitric acid. Add the saturated solution of 4.5 g of potassium ferrocyanide . Heat the solution until it acquires green color. Keep the green colored product in air for 2 hours It changes to blue. Filter the product, wash with a little alcohol, dry and weigh it.

7. Result : Yield of of Prussian Blue is 5.05 g.

8. Note Addition of 1-2 ml of K 2 Cr 2 3 will increase the oxidation öf green product. Prussian blue may also be obtained by the reaction of potassium ferrocyanide with ferric chloride. Prussian blue may be manufactured by roasting mixture of iron filings, potassium carbonate and organic proteinous matter. But no satisfactory yields

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