STUDIES ON THE METAL COMPLEXES OF HYDROXAMIC ACIDS. PART I. SPECTROPHOTOMETRIC DETERMINATION OF MANGANESE WITH NICOTINO- AND isoNICOTINOHYDROXAMIC ACIDS

Nicotino- and isonicotinohydroxamic acids are proposed as reagents for the spectrophotometric determination of manganese, by making use of the red-violet colour formed by the interaction of the metal with the reagents in ammania.cal medium at or above pH 9). The colour intensity is measured at 430-490 mμ for nicotino- and at 470-480 mµ for isonicotinohydroxamic acid. Beer's law is obeyd and the Sandell sensitivities are 0.014 \(\gamma\) for nicotino- and 0.013 \(\gamma\) for isonicotinohydroxamic acid. Job's methol indicates I : 3 comp!ex between the metal and the reagents. In the coloured products, manganese is believed to be in tervalent state. Copper, nickel, cobalt, silver and iron interfere seriously in the estimation of manganese. However, the first four interfering metals can be masked by sodium cyanide.

Picolinohydroxamic acid, curiously enough, exhibits only a faint red-violet colour under the same conditions, but fades rapidly.