In the isolation of metals,the calcination process usually results in:

Roasting of sulphides gives the gas $X$ as a byproduct. This is a colourless gas with a choking smell of burnt sulphur and causes great damage to respiratory organs as a result of acid rain. Its aqueous solution is acidic,acts as a reducing agent,and its acid has never been isolated.
The gas $X$ is

In metallurgy,calcination is used for .........

Explain Calcination and Roasting in detail.

What are the methods to convert concentrated ore into oxide? Explain them in detail.

Roasting involves