ASTM D1266 Test Method for Sulfur in Petroleum Products (Lamp Method)
11. Titration of Absorbent Solution
11.1 Add 3 to 4 drops of methyl purple indicator solution to the liquid in each absorber. Titrate the absorbent solution by introducing 0.05 N NaOH solution from a buret into the smaller bulb of the absorber. Use a 10-mL microburet if less than 10 mg of sulfur is expected to be present in the absorber. Stir during the titration by applying suction intermittently to the top of the larger bulb.
NOTE 12 - When incomplete combustion of the sample occurs, the air drawn through the absorber during the titration will have a characteristic taste or odor and the end point will be broad. In these cases, discard the determination.
12. Calculations
12.1 Calculate the sulfur content of liquid samples as follows:
Sulfur content, mass percent = 16.03 M x (A/10 W)
where:
A = millilitres of NaOH solution required to titrate the acid in the absorbent solution from the burned sample,
M = molarity of the NaOH solution (see Note 3), and
W = grams of sample burned.
12.2 When it is required by specifications to correct the sulfur content (Note 13) for lead antiknock fluids, calculate the corrected values as follows:
Corrected sulfur content, mass percent = S - LF
where:
F = 0.0015 if the sample contains aviation lead antiknock fluid or 0.0035 if the sample contains tetraethyllead, tetramethyllead, or the mixed lead alkyl antiknock fluid,
L = lead content, g/U.S. gal, and
S = sulfur content, mass %.
NOTE 13 - These corrections are based on experiments of burning fuels blended with antiknock fluid containing tetraethyllead and ethylene halide in commonly-used combinations. Tetramethyllead and the mixed lead alkyl antiknock fluids contain the same ethylene halide combination as the tetraethyllead fluid.
NOTE 14 - To convert grams of lead per Imperial gallon into grams per U.S. gallon, multiply by 0.8326. Multiply by 3.7853 to convert grams of lead per litre into grams per U.S. gallon.
