5. Examples of particle separation and identification using non-analytical ferrography

Although the non-magnetic particles are not sensitive to the magnetic field as they pass over the ferrograph, they are deposited randomly. The result is a ferrogram with two types of particles:

• magnetic particles ;

• non-magnetic particles.

These appear white and are indistinguishable by light microscopy. A few droplets of 0.1 mol/L acidic or basic solution are then deposited and the ferrogram is heated to 90°C using a hot plate. Some particles become soluble and, with increased heating, color changes are observed, depending on the type of metal. The various treatments and results are shown in Table 9 .