R. C. Wells V. North 1942 The well-known tendency of cobalt to be retained by the iron-alumina precipitate produced by ammonia has generally been ascribed to a specific adsorption by the large surface of this gelatinous precipitate. Whatever its cause, it can be overcome by precipitating the iron as phosphate at a pH of 3.5. The precipitate is easily filterable and practically all the cobalt passes into the filtrate. application/pdf 10.1021/i560111a012 en ACS Publications Use of phosphate for separation of cobalt from iron article