$(i)$ Name the process or the separation technique you would follow to separate:
$(a)$ Dyes in black ink
$(b)$ Butter from cream
$(c)$ Ammonium chloride and common salt
$(d)$ Iron filings and sand
$(ii)$ State the principle used in separation by centrifugation.

(A-D) $(i)$ $(a)$ Chromatography: This technique is used to separate solutes that dissolve in the same solvent.
$(b)$ Centrifugation: This method is used to separate suspended particles from a liquid based on density.
$(c)$ Sublimation: This process is used to separate a sublimable volatile component from a non-sublimable impurity.
$(d)$ Magnetic separation: This method is used to separate magnetic substances from non-magnetic substances.
$(ii)$ The principle of centrifugation is that when a mixture is rotated at high speed,the denser particles are forced to the bottom and the lighter particles stay at the top.