Compounds which are adsorbed to the more extent comes out later while the another one which absorbed to the less extent comes out readily. Since, compound ' $A$ ' comes out before compound ' $B$ ', the compound ' $B$ ' is more readily adsorbed on the column.

Silica (flux) being an acidic flux removes the impurities of iron oxide the basic impurity, by reacting with it. Thus, iron silicate (slag) is formed.

$$\underset{\text { Gangue }}{\mathrm{FeO}}+\underset{\text { Flux }}{\mathrm{SiO}_2} \longrightarrow \underset{\text { Slag }}{\mathrm{FeSiO}_3}$$

This is because oxides are reduced to metals easily while sulphides are not. So, sulphide ores are converted to oxide before reduction.

Zr and Ti are refined by van Arkel method. It involves 2 steps

(a) Formation of iodide e.g., zirconium

$$\mathrm{Zr}+2 \mathrm{I}_2 \longrightarrow \mathrm{ZrI}_4$$

(b) Decomposition of iodide

$\mathrm{ZrI}_4 \xrightarrow{1800 \mathrm{~K}} \underset{\text { Pure }}{\mathrm{Zr}}+2 \mathrm{I}_2$

During extraction of metals by electrochemical method the following two points must be considered

(i) Reactivity of metals If the metals are quite reactive and are expected to react with water then the metals should be extracted by the electrolysis of their purified molten ore rather than their aqueous solution.

(ii) Suitability of electrodes The electrods selected should not react with the product of electrolysis. If at all they react, then the electrodes must be made up of a material which is quite cheap since their periodic replacement should not increase the cost of the process.