What is solvent extraction ?
What is the main difference between cupellation and poling ?

Explanation

Solvent extraction is the latest separation technique and has become popular because of its simplicity and speed. The method is based on preferential solubility principles.
Solvent or liquid-liquid extraction is based on the principle that a solute can distribute itself in a certain ratio between two immiscible solvents, one of which is usually water and the other an organic solvent such as benzene, carbon tetrachloride or chloroform. In certain cases, the solute can be more or less completely transferred into the organic phase. The technique can be used for the purepose of preparation, purification, enrichment, separation and analysis.
Both cupellation and poling are used for refining of metals. In cupellation, impurities of other metals with traces of lead are removed from silver by heating impure silver with a blast of air in a cupel (an oval shaped pan made up of bone ash) in which lead is oxidized to lead oxide (PbO), which being volatile escapes leaving behind pure silver.
Poling is used for refining of such metals which contain impurities of its own oxide. In this process, the molten impure metal is stored with green wooden poles. At the high temperature of the molten metal, wood liberates methane which reduces the oxide of the metal to free metal.
`3Cu_(2)O + CH_(4) rarr 6Cu + 2H_(2)O + CO`