OCTOBER, 1949
541
LECTURE DEMONSTRATION OF ORE FLOTATION1 WILLIAM E. CALDWELL Oregon State College, Corvallis, Oregon
THE
flotation process has had marked success in the concentration of wanted metal sulfide containing minerals from unwanted siliceous or calcarious matter. Select,ive flotation attains separation of the various metal sulfides. Additional expansion of the flotation process of separating minerals is now in the field of nonmetallics; examples are flotation of calcium phosphate from siliceous impurity and even flotation of potassium feldspar from quartz. As use of the flotation process has expanded in industry, the importance of 'teaching the subject in a general chemistry course has increased. An accessory of good teaching is demonstration. Various supply houses manufacture small size laboratory test flotation cells. The metallurgical or chemical engiueering departments of most schools have such cells for flotation concentration of ore samples. Most of these test cells are of a size such that they can be carried to a chemistry lecture table. I t is suggested, then, that a chemistry department buy or borrow such a cell for lecture demonstration. A unit cell that has I m n found p r i ~ l usrfrt l in dcmonstrntiot~ to large: groups is thc Fapergrcn 1.nborntory Tcsr llarhint: of the .\rnerican Cyamr~iidCtmpnny, \~.lricl~ Hotntion tc>iringunit is hrrewith pictured. P For s~udcnt Iretun. (lt:n~un.itration\\XI proceed ,IS f l o . .\ f w pounds of gnlcnn (PbS) otr is ground to 100 mesh. Several pounds of fairly pure quartz (SiO*) is ground similarly. The ground materials are separately bottled. A mix of 50 g. ground galena to 350 g. of ground quartz is placed in a third bottle to simulate a lead sulfide-quartz ground ore. The 400 g. of galena and quartz mix is poured into about 2 liters of water in the bowl of the test machine, and thence agitation started. The pulp consistency and the ratio of sulfide mineral to siliceous gangue may vary considerably. Instead of compounding a specimen as here suggested, an actual sulfide ore may be ground for demonstration of flotation concentration.
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Presented a t the Symposium on Lecture Demonstrations hefore the Division of Chemical Education at the 115th Meetine of the American Chemical Society in San Francisco, March 27April 1, 1049.
t
Fagergren Laboratory Test Mashine
During initial agitation, an airentry pet cock on the vert,ical stem of the rotor is kept closed. Froma medicine dropper about 2 drops of a pine oil are added to the pulp and a pinch (mayhaps 0.1 g.) of some potassium xanthate. Some frothing occurs, but the main frothing and flow of surface froth over spillway into the catching container does not take place until the air pet cock is opened. I n use of a lead sulfide containing pulp, the froth will be definitely gray to black in contrast to the brown or whitish quartz material that will remain in the bowl. A cork in the bottom of the b o d may be removed to sample the bottom material. After demonstration of the flotation process the student is receptive to discussion of flotation.
