A metal ion found primarily in one of the three phases (oil, water, or dust) can serve as a marker for that phase. Emulsified water contains most of the magnesium detected in a shale oil. Extraction with saturated salt solution removes most of that Mg. The Mg content of retort water and the percentage of water in the oil (by ASTM D-4006) provides a good estimate of an oil's Mg content. Mineral matter elements with poorly water soluble carbonates (or oxides) at pH 8 (calcium, for example) serve as markers for dust. When the water is separated from the main and light oil fractions before adding the heavyfractioncontainingdust,a muchdrier oil can beobtained. However, when donein this way,a powdercontainingCa and Si remainsin the oil; it cannot be completelyremovedeven by filteringthrougha 0.24-p frit. Iron,and certainother transitionmetalions, isquiteoil soluble. Extractionwith dilutenitricacidto removebasic aminesreducestheFe contentof shale oil. Unlikecarboxylate-complexed metalions in crudeoils, the iron in shale oil does not extractefficientlyinto an aqueousEDTA solution(pH 5.9). Distillationof shale oil leavesmost of the iron and other metalsbehindin the vacuum residuum. Shaleoil corrodesthe hottestcondenser'ssteelinterior;this is thechief sourceof iron in the oil.