Spectrochemical analysis of tungstates

Abstract

The purity of tungsten as a raw material in hard metal has much influence on the properties of the products, especially on their cutting efficiencies. Excitation of tungstate was made by an A. C. arc at 220 V and 7 A with a Littrow type quartz spectrograph. The emission spectrum of tungsten was very complicated, and it was ac companied by many difficulties in spectrochemical detection of impurities. An addition of graphite. powder caused a suppressive effect on the appearance of the tungsten spectrum and made it much simpler. The suppressive action on the appearance of the tungsten lines by the addition of graphite was attributed to the formation of high boiling tungsten metal and tungsten carbide. This fact was made clear by X-ray analysis of the residue after arc discharge. Addition of graphite caused also a weakening in the spectral lines of the impurities. Therefore, attempts were made to add the salts of Na, Ge, Ba, Tl etc., as a carrier for the impurities in order to prevent the lowering of the sensitivity of them by the distillation of the carrier. Among those, BaCl₂: was the most effective as a spectroscopic carrier., Consequently, it was indicated that the impurities of tungstate could be easily detected without serious loss of sensitivities by addion of 5% BaCl₂ and graphite powder 5 times the weight of the sample.