STUDY AND APPLICATION OF NEW CHELATING TITRANT——DIRECT CHELATOMETRIC TITRATION OF Zn WITH TRIETHYLENETETRAAMINEHEXAACETIC ACID(TTHA)

A new method for direct chelatometric titration of Zn is studied. This method is based on the chelation of Zn with TTHA as titrant in aqeous medium and the end point is detected with 5-Br-PADAP-OP as metal indicator.It is shown that when the titration of Zn is in hexamethylene-tetramine buffer at pH 6.0—6.4, the indicator is very sensitive and a very sharp end point can be obtained.The relative standard deviation is 0.32%(n=10).The method has been successfully used to deter- mine Zn in lead-zinc ores,lead-zinc concentrates,zinc-base alloys and different kinds of samples containing Zn.