Radioactive Tests for Metals in Oils

Tests in which the radioactivity of metals or their compounds is used as a means of determining their presence or concentration are largely confined to experimental investigations. This  is true  because, first  activated metals or  compounds must  be present  and  this is not true of  commercial  lubricants and second, the life  of some of the  isotopes  used  is short so that  after  prolonged service the activity would  almost  disappear.