Mercury is purified by :

In the extraction of aluminium 

process $X$ : applied for red bauxite to remove iron oxide (chief impurity)

process $Y$ : (Serpeck's process) : applied for white bauxite to remove $Z$ (chief impurity) then,

process $X$ and impurity $Z$ are

Three most occuning elements into the earth crust are

In the cyanide process for extraction of gold and silver from ores, the cyanide solution acts as a

Method used for obtaining highly pure silicon used as a semiconductor material is