sentences:  The excess of EDTA is back-titrated with a suitable metal ion such as Mn2+ or Cu2+.At the endpoint, the first excess of metal ion catalyzes a strongly exothermic reaction between a polyhdric phenol (such as resorcinol) and hydrogen peroxide.Thermometric titrimetry is particularly suited to the determination of a range of analytes where a precipitate is formed by reaction with the titrant.