Outline the Volhard method for the titrimetric determination of chloride. Writethe stoichiometric equations of the precipitation reactions involved. Explain how the endpoint of the titration is detected and write the corresponding stoichiometric equation

The Volhard method is a titrimetric method used for the determination of chloride ions. It involves three main steps: precipitation, digestion, and titration.

1. Precipitation: The chloride ions in the sample are precipitated as silver chloride in the presence of nitric acid. The stoichiometric equation for this reaction is:

   AgNO3 + Cl- → AgCl(s) + NO3-

2. Digestion: The precipitate is then digested to ensure complete precipitation of chloride ions. This is done by heating the solution slightly and allowing it to stand for some time.

3. Titration: The excess silver ions are then titrated against a standard solution of ammonium thiocyanate. The silver thiocyanate formed is sparingly soluble and does not interfere with the titration. The stoichiometric equation for this reaction is:

   Ag+ + SCN- → AgSCN(s)

The endpoint of the titration is detected using ferric alum as an indicator. The ferric ions react with the excess thiocyanate ions to form a red-brown complex, indicating the end of the titration. The stoichiometric equation for this reaction is:

Fe3+ + 3SCN- → Fe(SCN)3

This method is very accurate and precise for the determination of chloride ions, but it requires careful handling due to the use of toxic reagents.