montana tech professor antoine marc gaudin defined the early period of flotation as the mechanical phase while by the late 1910s it entered the chemical phase. discoveries in reagents, especially the use of xanthates patented by minerals separations chemist cornelius h. keller, not so much increased the capture of minerals through the process as making it far more manageable in day to day operations. minerals separation's initial flotation patents ended 1923, and new ones for chemical processes gave it a significant position into the 1930s. during this period the company also developed and patented flotation processes for iron out of its hibbing lab and of phosphate in its florida lab. another rapid phase of flotation process innovation did not occur until after 1960.