On the Determination of Microamounts of Niobium in Iron and Steel by the Spectrophotometric Method

An experiment was carried out to establish a simple and accurate method for the determination of microamounts of niobium in iron and steel.The niobium was coprecipitated as pentaoxide with tungstic acid by the hydrolysis method with sodium sulfite and tannic acid in hydrochloric and perchloric acids to which 5 mL of sodium tungstate solution (1 mL=1 mgW) was added as coprecipitating reagent and was separated from other elements. By means of this separation method, the microamounts of niobium can be separated accurately from iron and others.The separated niobium was determined by the spectrophotometric method with xylenol orange.In this spectrophotometric method, there is no significant effect even in case 0.1 mg of alminum, 1 mg each of antimony, bismuth, iron, manganese, tin and zirconium, 0.02 mg of chromium, 0.5 mg each of cobalt, copper, nickel, phosphorus and tantalum, 20 mg of molybdenum, 5 mg of titanium, 0.2 mg of vanadium and 50 mg of tungsten are contained in the separated sample solution.As a result of the experiment, the author succeeded in establishing a method in which 0.005 to 0.05% of niobium in iron and steel can precisely be measured without difficulty.The niobium contents in synthetic and actual samples were measured by this method with satisfactory results.