UV/VIS-spectroscopy of liquid slags

UV/VIS-spectroscopical methods have been applied to investigate the absorpt ion behaviour of CaO-Al2O3-SiO2-slags in a wide temperature range from 20 t o 1655 degrees C. The observations reveal a strong temperature dependence o f the absorption bands, which can be explained by means of a newly develope d theoretical model. The model also correlates the observed long-frequency UV cutoff-wavelength with the optical basicity. The definition of the optic al basicity has been corrected for higher temperatures, since there are rem arkable deviations between the solid and the liquid state, which have not b een taken in consideration yet. Further investigations on a CaO-Al2O3-slag containing CaF2 at 1500 degrees C show that no. Fe3+... F--complexes like Fe3+(F-)(4) or Fe3+(F-)(6) are fo rmed. F- reacts with Al3+ forming Al-O-F-complexes. The F.-ions displace th e O2--ions from the Al3+. This causes the basicity to increase.