ACTIVE SULFUR IN FUELS AND SOLVENTS (DOCTOR TEST): ASTM D4952
(Equivalent Tests: IP 30 and ISO 5275)
EXPLANATION
Sulfur present as mercaptans or as hydrogen sulfide in distillate fuels and solvents can attack many metallic and nonmetallic materials in fuel and other distribution systems. A negative result in the Doctor test ensures that the concentration of these compounds is insufficient to cause such problems in normal use. This test is pertinent for petroleum product specifications given in Specification D235.
TEST SUMMARY
The sample is shaken with sodium plumbite solution, a small quantity of sulfur is added, and the mixture shaken again. The presence of mercaptans or hydrogen sulfide or both is indicated by discoloration of the sulfur floating at the oil-water interface or by discoloration of either of the phases.
TEST PRECISION
Since this is a pass-fail test, no estimates of precision or bias can be made.
