Argentometric titrations are titrations involving silver nitrate (AgNO3) as the titrant, typically used for the determination of halide ions such as Cl−,Br−, and I−. One common method is the Fajans method, where an adsorption indicator, such as fluorescein or eosin, is used. Before the equivalence point, halide ions are present in excess, and the precipitate surface (AgX) is negatively charged. After the equivalence point, excess Ag+ions make the surface positively charged, allowing the negatively charged dye ions (like eosin) to adsorb on the surface and cause a visible color change - signaling the end point. Hence, Eosin dye (an adsorption indicator) is used in argentometric titrations by Fajans' method.
