why does the solvent becomes cloudy when you add ligroin to acetone solution of caffeine during crystalization

Answer 1

Caffeine is soluble in acetone, especially warm acetone.

Ligroin is a mixture of hydrocarbons. Caffeine is not very soluble in hydrocarbons.

When ligroin is added to an acetone solution of caffeine, the caffeine becomes less soluble in the solvent mixture and so starts to precipitate out as a solid. This is the "cloudy" effect.

If the solution is then cooled, even more caffeine comes out of solution and this the the material collected.