In analytical chemistry, argentometry is a type of titration involving the silver(I) ion.
Calcium acetate "fixes" free chlorine, precipitates carbonates, and neutralizes the resultant solution.
Past the equivalence point, excess silver(I) ions adsorb on the AgCl surface, imparting a positive charge.
Anionic dyes such as dichlorofluorescein are attracted to the particles, and undergo a colour change upon adsorption, representing the end-point.
Eosin (tetrabromofluorescein) is suitable for titrating against bromide, iodide, and thiocyanate anions, giving a sharper end-point than dichlorofluorescein.