Monoclonal antibody (MW = 155,000 kg-moles/m3) is being purified from hybridoma cell culture supernatant by ammonium sulfate precipitation. The antibody concentration in the starting material is 0.5 g/1 and 30% of the antibody could be precipitated using 1 M ammonium sulfate cut. What salt concentration would have resulted in 90% precipitation of the monoclonal antibody? The solubility of the antibody in salt free water is 390 g/1.