Question

Fucntion of citric acid in limit test for iron

Answer 1

● Citric acid catalyzes the reaction in limit test of iron.

● Citric acid helps precipitation of iron by smelling salts like ammonia by framing a complex with it.

● Limit test of Iron depends on the response of iron in ammonical arrangement with thioglycollic corrosive in presence of citric acid to shape iron thioglycolate which is pale pink to profound ruddy purple in shading.

Answer 2

Citric acid functions as the chelating agent in the limit test for iron and binds with the iron to form a soluble complex.

Explanation:

• The limit test for iron is based on the reaction of iron (in ammoniacal solution) with thioglycolic acid in the presence of citric acid.  
• Iron-free citric acid is used in the limit test for iron. The citric acid acts as a chelating agent, binds with iron and forms a soluble complex with the iron.
• Citric acid also prevents formation of ferrous hydroxide due to precipitation by ammonia.
• Citric acid also has a nature of binding with other metal cations and hence it prevents interference of any other metal.