Education of the republic of uzbekistan tashkent state technical university named after islam karimov

O
3
 + ZnO 
Figure 8. Diagram of the change in the value 
of the free energy of the reaction 
CaO + SiO
2
 = Ca
О∙
SiO
2
 
Figure 9. Diagram of the change in the value of the free energy of the reaction 
CaO + Fe
2
O
3
 =Ca
О∙
Fe
2
O
3
When performing this research work, it was found that at oxidative roasting temperatures 
of 945-995 °C on individual grains of sulfide minerals, the temperature rises above 1200 °C, 
which leads to the melting of these grains. As a result of the melting of mineral grains, complex 
compounds are formed, similar to metallurgical slags (zinc ferrites and silicates). In this regard, 
to the processes of formation of ferrites and zinc silicates during oxidative roasting, the 
formation laws of metallurgical slags can be applied to some extent. 
According to the molecular theory of the formation and structure of liquid slags, 
substantial oxides displace from chemical compounds weaker ones, which remain in the melt in 
a free state. The "strength" of an acidic or basic oxide in a melt can be measured by the 
thermodynamic potential for the formation of compounds from the oxides. 
The greater the value of the thermodynamic potential (its negative value), referred to as 1 
mole of acidic oxide, the more "strong" the base and the more firmly its connection with the 
acidic oxide. 
The most substantial bases in silicate melts are oxides of alkali and alkaline earth metals 
Na
2
O, K
2
O, CaO, MgO, and BaO; the weaker bases are heavy metal oxides: FeO, MnO, PbO, 
Cu
2
O, and NiO, and the weaker ones are amphoteric: ZnO, Fe
2
O
3
, Al
2
O
3
. The most vital acidic 
oxide in slags is SiO
2
. 
Thus, “strong” basic oxides and “strong” acidic oxides form the most thermodynamically 
vital compounds, and “weak” basic oxides with weak acidic ones form thermodynamically 
unstable chemical compounds. Based on this, it can be assumed that introducing "strong" basic 
oxides into the roasting mixture will decrease the formation of ferrites and zinc silicates. 

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