The Ferro-Ham chloranilic acid precipitation method for calcium uses which acid as reagent?

• A. Chloranilic acid
• B. Oxalic acid
• C. Sodium tartrate
• D. Potassium permanganate

Answer: (A)

The key idea is that calcium is precipitated as a calcium–chloranilate complex by reacting with chloranilic acid in the Ferro-Ham method. Chloranilic acid specifically forms an insoluble complex with Ca2+, which allows the calcium to be separated from the solution for gravimetric determination. This makes chloranilic acid the reagent used in this method.

Oxalic acid would give calcium oxalate instead, and sodium tartrate would form calcium tartrate, neither of which describes the Ferro-Ham precipitation. Potassium permanganate is an oxidant and not used to precipitate calcium in this procedure.