Spectrographic determination of impurities in ultrapure tungsten and tungsten oxide.
The effects of an external magnetic field and of the diameter of the anode on the spectroscopic line intensity of the impurity elements in ultrapure tungsten and tungsten oxide have been studied. The results obtained are used for the development of a more sensitive method for the determination of these impurities (Mn, Pb, Fe, Ni, Al, Mo, V, Cu, Cr).
The use of external magnetic fields in spectroscopic analysis of traces in DC arc
SummaryThe use of external magnetic fields leads to an increase of intensity of spectral lines of traces. This makes possible the elaboration of new methods for spectrochemical trace analysis. The intensification of lines is connected with the broad shape of the arc plasma and with the residence time of particles in it.ZusammenfassungDurch Anwendung von Fremdmagnetfeldern kann eine Intensitätserhöhung der Spektrallinien von Spurenelementen im Lichtbogen erreicht werden. Dadurch ergibt sich die Möglichkeit der Entwicklung neuer spektrochemischer Verfahren zur Spurenanalyse.Die Intensitätserhöhung der Spektrallinien steht im Zusammenhang mit der breiten Plasmaform und der längeren Verweilzeiten der Teilchen im Bogenplasma.
Effects of the mineral phase and valence of vanadium on vanadium extraction from stone coal
The influence of roasting on the leaching rate and valence of vanadium was evaluated during vanadium extraction from stone coal. Vanadium in stone coal is hard to be leached and the leaching rate is less than 10% when the raw ore is leached by 4 mol/L H2SO4 at 90°C for 2 h. After the sample is roasted at 900°C for 2 h, the leaching rate of vanadium reaches the maximum, and more than 70% of vanadium can be leached. The crystal of vanadium-bearing mica minerals decomposes and the content of V(V) increases with the rise of roasting temperature from 600 to 900°C, therefore the leaching rate of vanadium increases significantly with the decomposition of the mica minerals. Some new phases, anorthite for example, form when the roasting temperature reaches 1000°C. A part of vanadium may be enwrapped in the sintered materials and newly formed phases, which may impede the oxidation of low valent vanadium and make the leaching rate of vanadium drop dramatically. The leaching rate of vanadium is not only determined by the valence state of vanadium but also controlled by the decomposition of vanadium-bearing minerals and the existence state of vanadium to a large extent.