A host of inorganic pharmaceutical substances essentially
containing polyvalent and bivalent metal ions, for instance : Al3+,
Ca2+, Mg2+, Bi2+ and Zn2+ were
initially analysed quantitatively by the aid of gravimetric methods.
These historically important procedures have become more or less obsolete since
they are extremely time consuming and
tedious owing to several steps involved e.g.,
precipitation, filtration, washing, drying and finally ignition to a constant
Thereafter, analysis was done by faster techniques based
on oxalate-permanganate titrations which involved a precipitation procedure
followed by quick titration of pre-heated solutions containing oxalate ions.
More recently the introduction of an analytical reagent
disodium ethylene-diaminetetraacetate, invariably termed as EDTA, an altogether latest titrimetric
method has been used exclusively for the estimation of metals using metal-ion indicators.