1.1 ,This test method covers a method suitable for measuring the total amount of hydrogen sulfide (H₂S) in heavy distillates, heavy distillate/residual fuel blends, or residual fuels as defined in Specification D396 Grade 4, 5 (Light), 5 (Heavy), and 6, when the H₂S concentration in the fuel is in the 0.01 ,μ,g/g (ppmw) to ,100 ,μ,g/g (ppmw) range.