This dissertation presents the results of research on the flotation system potassium n-amyl xanthate - sodium sulfide - molybdenite. The purposes of the research were (1) to determine the theoretical collector-depressant equilibria conditions of this system necessary for the flotation or depression of molybdenite, (2) to ascertain the mechanism of adsorption or the collector potassium n-amyl xanthate and the depressant sodium sulfide on molybdenite, and (3) to calculate the standard free energy of adsorption on molybdenite of the collector and depressant in this system. To accomplish these purposes it was necessary to develop a satisfactory experimental method for the controlled testing of collector and depressant action in this system. Because of the physical properties of molybdenite, attempts to employ the methods of other investigators were unsuccessful. The experimental method finally devised was a modification of the "captive bubble" technique of Wark and Cox. The smooth surfaces of pressed molybdenite pellets were used in place of polished mineral surfaces. Tables 1 and 2 list the data obtained in ascertaining the collector-depressant equilibria conditions of this system and Figures 5, 6 and 7 are plots of these data. Strong evidence was given in support of the Cook hydrolytic free acid absorption theory, and it was found that the Cook single site free acid model best describes the adsorption ef n-amyl xanthic acid and hydrosulfuric acid on molybdenite. The adsorption potential for the adsorption of hydrosulfuric acid on molybdenite at 25°C. was calculated to be -11,548 cal./mole. The adsorption potential for the adsorption of n-amyl xanthic acid on molybdenite was calculated to be -15,173 cal./mole assuming 25 % surface coverage and -15,826 cal./mole assuming 50 % surface coverage.



College and Department

Chemistry and Biochemistry



Date Submitted


Document Type





Molybdenite, Flotation