'The investigation of the use, as analytical precipitants, of a number of aromatic phenyll~ydrosylamines is described. In general they react similarly, increasing in selectivity with an increase in acidity of the oxime group. In acid solutions (lye or more) only vanadium, tin, titanium, and zirconiun~ are precipitated. Their variation in reaction with copper and the nature of their reaction with tin are described. All conlpounds can act as osidants or reductants with an oxidation potential of approsimately -1.2 volts.
INTRODUCTIONT h e use of cupferron [C6H5NO(NH4)NO] as an analytical precipitant was first proposed by Baudisch (1). I t is most useful in acid medium for the quantitative precipitation of iron, titanium, zirconium, vanadium, and tin; elements such as aluminum, chromium, manganese, nickel, cobalt, and the alkaline metals with which they are usually associated do not interfere. A marked disadvantage of cupferron, however, is its instability. In addition, complexes precipitated by this reagent cannot be weighed as such but must be ignited t o the oxides.* Schonle (4), by substituting a benzoyl for the nitroso group of cupferron, obtained a co~npound that was stable, and formed conlplexes with iron, alunlinum, and copper that could be dried a t llO°C. Ryan and Lutwick (3) extended the use of N-benzoylphenylhydroxylamine to the gravimetric determination of tin. The tin complex was dried a t llO°C. and weighed as [ ( C~~H~O N O Z ) Z S~C I ? I .The low solubility of the N-benzoyl derivative of phenylhydroxylamine in water necessitates close control of excess reagent and its basicity prevents the preparation of an ammonium salt. For these reasons a number of N-substituted phenylhydroxylan~ine compounds, containing a carbonyl alpha t o the oxime, were prepared and their reactivities investigated.
COMPOUNDS INVESTIGATEDT h e following (mono-) N-derivatives of phenylhydroxylamine were pre-0 0 11 Il
