Recently, N-bcnzoyl-o-tolylhydroxylaminel (I) and N-benzoyl-$-chlorophenylhydroxylaminea (II) have been proposed as spectrophotometric reagents for the clctermination of vanadium. Of these reagents, the former under suitable experimental conditions behaves as a specific reagent for vanadium and the latter is highly selective in its reaction.
Further investigation under the same conditions has shown that N-phenylacetylphenylhydroxylamine (III), N-benzoyl-nz-tolylhydroxylamine (IV) and Nbcnxoyl-$-tolylhydroxylamine (V) have similar characteristics to theo-tolyl derivative. The former forms a reddish violet complex while the latter two form violet complexes with the vanadatc ion. These colourcd complexes on extraction with chloroform from strong hydrochloric acid solutions, form the basis of highly sensitive and specific methocls for the determination of vanadium (Table I). The colour intensities of the complexes formed under these conditions are greatly reduced, and can even be changed to different hues, in the presence of even traces of alcohol; the chloroform used for extraction must therefore be free from alcohol.
However, in the presence of alcohol, all the 5 reagents were found to form yellow coloured complexes at a PH of 4.8~G.o. These complexes on extraction with chloroform from a buffered acetic acid-sodium acetate solution show absorption maxima at 440 mp. These coloured systems obey Beer's law from 1-x2 pug of vanadium with optimum ranges from 3-12 ,ug of vanadium. The percent relative errors in these regions are 2.736 with the reagents (I), (IV) and (V), and 2.715 and 2.726 with the reagents (III) and (II) respectively.
ESI'ERIMEN'TAI.
The reagents IV and V were prepared in the same way as proposed for the o-tolyl derivativel, These colourless reagents were purified by recrystallisation from aqueous alcohol (m-p. 7o" and xoQ", respectively.
Found: C, 73.96; H, 5.84; N, 6.22% for (IV) and C, 74.02; H, 5.70; N, 6.13% for (V); calculated: C, 74.08; H. 5.72; N, 6.16%).
Reagent III was prepared from nitrobenzene and phenylacetyl chloride. First the nitrobenzene was reduced by zinc dust to phenylhydroxylamine, which was then coupled with phenylacetyl chloride as described previouslys. The product was re-