This International Standard specifies a procedure (Doctor test) for the detection of thiols (mercaptans), hydrogen sulfide and elemental sulfur in hydrocarbon solvents and distillate petroleum feedstocks and products. Preliminary procedures also detect the presence of peroxides and phenolic substances, which, when present in more than trace quantities, make the application of this International Standard inappropriate. Carbon disulfide, at relatively high concentrations [above 0,4 % (m/m) sulfur], also interferes with the interpretation of the test by causing darkening of the aqueous layer.
NOTE For the purposes of this International Standard, the term “% (m/m)” is used to represent the mass fraction of a material.
The test is a go/no-go procedure with a threshold value of thiol concentration dependent on the material under test. It is frequently used as a substitute for the quantitative determination of thiol content.