Question

How does a metal indicator work for EDTA titration?

Answer 1

An EDTA titration can be used to determine the concentration of metal ions in a substance. For example the Nickel content in a salt. In this experiment the indicator used is murexide indicator which binds less strongly to the Nickel ions than EDTA so when the reaction is complete (all the Nickel is used up) the volume of EDTA used can then be used to determine concentration of metal ions. This ability that EDTA possesses to bind to metal ions is due to the lone pairs of electrons in its structures so it can chelate the ions. It must be done under basic conditions so H+ are not attracted to lone pairs.

As a side note EDTA has good uses in medicine for example if someone overdoses on iron tables they undergo chilation therapy. It is becoming increasing important in areas such as medical negligence and court cases. It can be used to determine is hip implants were faulty by testing for various ions in blood.