In a recent investigation of the reactions of a large variety of hydroxamic acids with metal iorisl~", it became apparent that vanadium(V) has a high degree of rcnctivity with most of them. In particular, 2-naphthohydroxamic acid in methanol gives an intense and stable red-orange color with vanadium. This metal is a widely occurring element often in trace concentrations, and is found in plants, soils, clays, animal tissue and bone, and in many steels and non-ferrous alloys. 2-Naphthohydroxamic acid was synthesized for our study; its analytical properties have not been reported. Lt was therefore decided to examine the color reaction bctwecn vanadium(V) and a-naphthohyclroxamic acid and to develop a new reagent for the spectrophotometric determination of vanadium.
Several hydroxamic acids have been used for the analysis of vanadium, among them benzohydroxamic acida-0, N-phcnylbcnzohydroxamic acid'-0, and N-cinnamoyl-N-phenylhydroxylaminc 1". Other frequently used reagents for vanadium include di-phenylbenzidinel~ and cupferronln. The high sensitivity of a-naphthohydroxamic hcid for vanadium and the usefulness and simplicity vanadium in a variety of materials indicates that it those reported in the literature. * Since the reaction was carried out in methanol, with only a very small amount of water prcscnt, the true per of the solution could not bc dctcrmincd; hcncc the acidity values obscrvcd throughout the investigation are pII-mctcr readings rather than actual per values.