Stabilization and Sensitization of Ferric Thiocyanate Colour for Determination of Trace Amount of Iron in Zinc Oxide and other Zinc Minerals

Abstract

The effect of various ketones and ketonic mixtures on the stability and sensitivity of ferric thiocyanate colour in aqueous solution has been systematically studied. Maximum increase in intensity (about 2 times) and stability (more than 4 hours) of the coloured complex has been observed in aqueous solution containing a mixture of methyl ethyl ketone and acetone in the ratio from 2:1 to 1:2 and having an overall pH from 1.4 to 1.7. Below pH 1.4, the ferric thiocyanate colour separates out in the upper layer of the solution while its stability and intensity of colour decrease with the increase of pH above 2.7. Large amounts of zinc which interfere with the determination of iron by orthophenanthroline method do not have any adverse effect on the ferric thiocyanate colour. Based on these observations, a simple and sensitive procedure has been worked out for determination of small amounts of iron in zinc oxide and other zinc minerals.