Spectrophotometric determination of hydrazine using bromine and methyl red

Hydrazine has been determined by its oxidation to nitrogen with a known excess of bromine. Bromine in acidic medium bleaches the dye methyl red. A known excess of bromine when treated with hydrazine is reduced to bromide and the unreacted bromine is determined using methyl red. The molar absorptivity is calculated to be 9.95 x10 L molcm. The method obeys Beer’s law in the range 0-6 μg of hydrazine in an overall aqueous volume of 25 mL with a correlation coefficient of 0.999.The detection limit is 0.25μg of sample. The relative standard deviation is 2.7% (n=10) at 3 μg of hydrazine. Interferences due to various foreign ions have been studied. The proposed method has been successfully applied for the estimation of hydrazine in boiler feed water samples. The results obtained in the developed method compare well with the p-dimethylaminobenzaldehyde (p-DAB) method and by the recovery studies of added hydrazine.