Murine monoclonal antibody is to be recovered from 100 liters of cell culture supernatant having antibody concentration of 0.2 kg/m3 by ammonium sulphate precipitation. MW of antibody = 155 kDa and MW of (NH4)2SO4 = 132 kg/kgmole. How many kilograms of ammonium sulphate would be needed to precipitate 95% of the antibody? A preliminary experiment carried out using 1 liter of a similar cell culture supernatant showed that 180 mg of the antibody could be precipitated at 1.75 M ammonium sulphate concentration. The solubility of the antibody in salt free water is 390 kg/m3 .