Abstract
	Optical emission spectral analysis method enables to analyse the solid samples. The relationships of the spectral line intensity and the evaporation period of the sample into plasma are expressed in the form of the evaporation curves. These curves when linked with the calculations of Gibbs energy change values of the assumed chemical reactions enable to assess the processes occurring in plasma. The tests have been carried out with the synthetic sample which according to its composition corresponded to the composition of the inorganic portion of the outcome slurry from the waste water cleaning plant. Process of the fractional distillation existing in the course the electrode evaporation has been simulated using the spectrochemical additives as follows: graphite powder, litium carbonate, barium nitrate and cobalt fluoride.
	The measurements and calculations has been carried out for the analytes having variable ability to evaporate into plasma as follows: oxides of silicon, vanadium, titanium, chromium.
	The present work has confirmed that cobalt fluoride considered as the typical fluorinating additive, is stable up to 5000 K, i.e. it is an inert additive, which influences the evaporation process only in the mixture with the active additive, as for example barium nitrate. Proposed have been three mechanisms of the element evaporation out of oxides into plasma.
Oxide evaporation into plasma and subsequent reduction of refractory oxide into volatile metal.
Metal reduction in oxide in refractory metal or refractory carbide origin.
Oxide reduction in metal in the elektrode and it evaporation into plasma