Paraformaldehyde as an end-point indicator in hydrolytic thermometric titration of metal ions and iodine

The use of paraformaldehyde (PF) as an end-point indicator in hydrolytic titrations involving precipitation, complexation and redox reactions was investigated. The decrease in temperature caused by depolymerization of PF, catalysed by hydroxyl ions produced by hydrolysis of excess of titrant, was employed to locate the end-point of the titration. The results of titrations of alkaline earth metals with carbonate, several metal ions with EDTA and iodine with arsenite are presented.