Let's say you want to prepare barium sulphate 1) 20 cm3 of 0.5 mol dm-3 ba.chloride sol is added to 20 cm3 of 0.5 mol dm-3 sod.sulphate sol in a beaker 2) The mixture is stirred thoroughly with a glass rod. A white precipitate is formed immediately. 3) The mixture is filtered to obtain the white barium sulphate as the residue 4) The residue is rinsed with distilled water and dried using filter paper