Question

In the extraction of silver by Mac-Arther cyanide process, a small amount of $K{NO}_3$ is also added as flux. The function of $K{NO}_3$ is:

• A. to oxidise $Ag$ in the native from to ${Ag}^{+}$
• B. to oxidise lead and zinc impurities
• C. to form a complex with ${Ag}^{+}$ which is then reduced to metallic silver by using zinc
• D. to oxidise the sulphur in the argentite ore to ${SO}_2$ which escapes from the reaction

Answer 1

The correct option is B to oxidise lead and zinc impurities

$K{NO}_3$ oxidizes lead and zinc impurities. hence a small amount of $K{NO}_3$ is added as flux during extraction of silver by Mac-Arther cyanide process.