Leaching Process - Practice Questions & MCQ

In this method, the powdered ore is treated with a suitable chemical reagent which dissolves the ore while impurities remain insoluble in that reagent.
For example: 
Bauxite is separated from Fe₂O₃, SiO₂, TiO₂, with the help of NaOH in which Al₂O₃ gets dissolved while rest are insoluble.
For example:

The sodium aluminate present in solution is neutralised by passing CO₂ gas and hydrated Al₂O₃ is precipitated. At this stage, small amount of freshly prepared sample of hydrated Al₂O₃ is added to the solution. This is called seeding. It induces the precipitation.

Sodium silicate remains in the solution and hydrated alumina is filtered, dried and heated to give back pure Al₂O₃.