(a) What is meant by the term 'purification' and what does it 'separate'? (3)

(b) What are the basic methods of 'separation'? Explain the functioning of 'purifier' and 'clarifier'? (3)

(c) What is meant by the term 'interface' and what is the role of 'gravity disc' in determining the same (4)

(d) What is 'NOMOGRM' and how correct 'gravity disc' size is selected (6)