2626.     PETERSEN, W.  [Effect of Phenol Content of Flotation Agents in Treatment of Coal Fines.]  Bergbau Arch., vol. 8, 1948, pp. 88-103; British Abs., November 1948, B, I, p. 580.

        Tar-oil fractions for flotation should contain 4-5% of phenols to promote frothing.  Part of the phenois can be supplied by addition of limited amounts of ammoniacal spent liquor containing about 1.8 gm. of phenols/l.  Still greater economy of tar oil can be achieved by addition of pine oil.  Paraffin is inferior to tar oils unless improved by frothing agents.  A synthetic Fischer-Tropsch oil fraction containing no phenols, but 0.7% of saponifiable constituents, when tested in progressively increasing amounts, was comparable initially with tar oils, but its efficiency was not maintained at higher concentrations.