1.1 ,This method covers a procedure for determining the concentration of compounded forms of iron in in-service fluids. It is applicable over an iron concentration range of 20 ,mg/kg to 800 ,mg/kg (ppm by mass hereafter). The test is not sensitive to metallic iron and thus provides a means of discrimination between the two forms of iron. It is suitable for monitoring the condition of equipment where iron contamination in the lubricating oil or functional fluid may not originate solely from physical wear, for example from corrosion or other forms of undesirable chemical processes within the equipment.