Formalin and paraformaldehyde as end-point indicators in catalytic thermometric titrimetry

The use of formalin solution as an end-point indicator in the titration of both acids and bases in aqueous solutions was investigated. In both instances, a lowering in temperature at the end-point, due to depolymerization of poly(oxymethylene glycols), was observed. Endothermic end-points were also obtained by using paraformaldehyde as an end-point indicator in titrations of acids in aqueous solutions. The use of paraformaldehyde in the titration of very weak acids and of some sparingly soluble acids solubilized in micellar suspensions of cationic detergents was also investigated.