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# Which of the following processes best describes the purification of muddy water by addition of alum?

(a) Absorbtion

(c) Dialysis

(d) Coagulation

Can you answer this question?

Alum is a double sulphate of potash and aluminium, and in this case breaks into potassium sulphate which remains in solution, and a basic aluminic sulphate. This basic sulphate of aluminium, the composition of which is undetermined, precipitates as a more or less gelatinous and flocculent mass, and carries down with it the foreign matters and humus bodies.
By the addition of a minute amount of alum, water is rendered capable of a most perfect jnechanical filtration.

answered Dec 14, 2013