Davis Tube electromagnetic separators create a magnetic field which is able to extract magnetic particles from pulverized ore. With this instrument the percentage of magnetic and non-magnetic material in a sample may be determined. Further chemical analysis may be performed on these fractions for more detailed information about composition.
A 30g aliquot of pulp sample is gradually added to the cylindrical glass tube which oscillates at 60 strokes per minute. As the sample progresses down the inclined tube the magnetic particles are captured by the magnetic field. Wash water flushes the non-magnetic fraction out of the tube until only the magnetic fraction remains. Both the magnetic and non-magnetic fractions are dried and weighed to determine the percentage of magnetics in each sample.