N-Aryl Hydroxamic Acids as Gravimetric Reagents for Niobium and Tantalum

Twenty six newly synthesized N-aryl-hydroxamic acids have been examined as reagents for gravimetric determination of niobium and tantalum. N-Phenyl-p-ter-butylbenzohydroxamic acid was found to be the most suitable rea~ent in the series examined and is proposed for the separation and gravimetric determination of niobium and tantalum. Niobium and tantalum are precipitated in the pH range of 3.5-6.5 and 0.8-1.8 respectively. The niobium and tantalum hydroxamates are ignited to oxides and weighed .as niobium pentoxide and tantalum pentoxide. Niobium has also been estimated by direct weighing of the niobium hydroxamate. Separation of niobium and tantalum has been achieved using N-phenyl- p-ter-butylbenzohydroxamic acid by adjusting the pH of precipitation, without using any masking agent