ASTM D4628 for barium, calcium, magnesium and zinc in unused lubricating oils
ASTM D4628 standard test method for analysis of barium, calcium, magnesium, and zinc in unused lubricating oils by atomic absorption spectrometry
3. Summary of Test Method
3.1 A sample is weighed and base oil is added to 0.25 more or less 0.01-g total mass. Fifty millilitres of a kerosine solution, containing potassium as an ionization suppressant, are added, and the sample and oil are dissolved. (Warning - Hazardous. Potentially toxic and explosive.) Standards are similarly prepared, always adding oil if necessary to yield a total mass of 0.25 g. These solutions are burned in the flame of an atomic absorption spectrophotometer. An acetylene/nitrous oxide flame is used. (Warning - Combustible. Vapor harmful.)
4. Significance and Use
4.1 Some oils are formulated with metal-containing additives that act as detergents, antioxidants, antiwear agents, etc. Some of these additives contain one or more of these metals: barium, calcium, zinc, and magnesium. This test method provides a means of determining the concentration of these metals that gives an indication of the additive content in these oils.
