Analytical Applications of Phenylhydrazine Sulphinic Acid for Determination of Molybdenum and Copper

Chemical Laboratories, Directorate of Geology & Mining, Raipur, (M. P.)

Department of Chemistry, Government College of Science, Raipur, (M. P.)

Manuscript received 17 January 1977, revised 18 May 1978, accepted 22 December 1978

A rapid spectrophotometric method for the determination of trace amounts of molybdenum has been developed using phenylhydrazine sulphinic acid. An aqueous solution of the reagent develops a red colour with molybdate ions in acetic acid media ranging from 10 to 70% by volume. The intense red colour produced has its maximum absorbance at 510 nm. Sandell's sensitivity of the colour reaction is 0.012 µg of molybdenum cm². The system conforms to Beer's law over the concentration range of 0.6 to 6 µg per ml of molybdenum and has a molar absorptivity of 8.0 x 10² litre mole^-1cm^-1. Investigations have indicated that the reagent is a useful alternative for sulphurous acid in the determination of copper as copper(I)-thiocyanate.