What is self-reduction in metallurgy? Give example.

Explanation

Self reduction (Auto-reduction) : During the process of roasting , the sulphides of same metals like Cu, Pb nd Hg are partly converted into corresponding oxides . These metal oxides reduce the remainig metal sulphides into corresponding metals . This process of reduction is called self redution .
In case of copper pyrite or copper glance,
`2Cu_2S + 3O_2 rarr 2Cu_2O + 2SO_2` ,
`2Cu_2O + Cu_2SoversetDelta rarr6Cu + SO_2` ,
In case of lead from galena ,
`2PbS + 3O_2 rarr 2PbO + 2SO_2`
PbS + 2PbO `rarr` 3Pb +` SO_2`