Canadian mining journal July-December 1915 . der, made of con-ducting material, such as iron, about half immersed ina clay pulp in a trough. At a distance id about L. the immersed side of the cylinder is a coarse wirescreen. A direct current of about 50 volts was appliedto the cylinder and the screen, the cylinder being theanode and the screen the cathode. The cylinder at-tracted the negatively charged kaolin, while the screenattracted the positively charged pyrite, ferric hydroxide,and aluminum hydroxide. It Was found that a productrunning only about 17 to 20 per cent, moisture couldb
Canadian mining journal July-December 1915 . der, made of con-ducting material, such as iron, about half immersed ina clay pulp in a trough. At a distance id about L. the immersed side of the cylinder is a coarse wirescreen. A direct current of about 50 volts was appliedto the cylinder and the screen, the cylinder being theanode and the screen the cathode. The cylinder at-tracted the negatively charged kaolin, while the screenattracted the positively charged pyrite, ferric hydroxide,and aluminum hydroxide. It Was found that a productrunning only about 17 to 20 per cent, moisture couldbe scraped off the upper side of the cylinder, which re-volved slowly, while the imparities fell through thescreen to the bottom of the trough The objection to «« (1912-13). 7LL» THE CANADIAN MINING JOURNAL December 1. 1915 the process was the high cost of the power needed, whichaveraged, as I remember it, over 30c per ton of product,but the process is undoubtedly of interest in that itshows that these electrostatic charges are dependable. a Revolving cylinder 6 Wire screer C Wood trougl. d Clay pulp Fig. 7—Apparatus used in purifying clays enough to be put to practical uses. It is also of interestin that the polarity of the charges noticed on variousminerals checks the results of the experimental workupon which this theory is based. Oliver C. Ralston, Salt Lake City, Utah.—Perhaps themost interesting part of Mr. Callows paper is the refer-ence to a theory of flotation founded on the electriccharges of the ore particles, oil droplets, air bubbles,etc., involved. For some time I have had a growing conviction thatpossibly the particles dealt with in the flotation of sul-phide minerals were acting according to certain lawslaid down in colloid chemistry. One of the characteristicthings about either suspension or emulsion colloids isthat their individual particles are charged with one orthe other sign of static electricity. It is known that theamount and signs of these charges
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