Precipitation Titration: Overview

In precipitation titrations, the analyte mixed with visual indicators reacts with the titrant to form a colored precipitate or a soluble, colored complex at the endpoint.

A popular precipitating reagent is AgNO₃ used in silver or argentometric titrations.

A precipitation titration curve monitors the analyte or titrant concentration—plotted as the p function—against the titrant volume.

Consider the titration of Cl^- with AgNO₃.

In the beginning, the free analyte concentration is high. With the addition of titrant, some analyte is consumed, and AgCl is precipitated.

The titration plot defines three regions. In the pre-equivalence region, the concentration of the unreacted analyte is determined from the moles of excess analyte and the total volume.

At the equivalence point, the partial redissolution of the precipitate generates equal concentrations of silver and chloride ions, and the analyte concentration is calculated from the solubility product.

Beyond the equivalence point, the analyte concentration is determined from the solubility product, where the Ag⁺ concentration is obtained from the excess moles of the titrant.