ASTM D5705 Test Method for Measurement of Hydrogen Sulfide in the Vapor Phase Above Residual Fuel Oils
11. Calculation and Report
11.1 Determine the average of the readings from the duplicate test samples and report the average H2S concentration in micromoles per mole (parts per million (ppm v/v)) for each test along with the test temperature.
12. Precision and Bias
12.1 Precision - The precision of this test method as determined by statistical examination of interlaboratory test results is as follows:
NOTE 7 - The precision data were developed in a 1993 two-phase cooperative testing program. Each phase involved four fuels tested by eight participants in four locations. Since samples could not be shipped too far and could not be kept for different time periods before testing, the four locations were in a specific geographic area for each phase. All participants tested each sample on the same day. All participants ran each fuel oil four times using separate samples and fresh detector tubes. The first two results were averaged, and the last two results were averaged. The two average numbers were used to derive the precision statement. Five of the participants in Phase 1 were also in Phase 2. The fuels tested had hydrogen sulfide contents between 9 µmol/mol (ppm v/v) and 4000 µmol/mol (ppm v/v) and a viscosity range from 80 mm2/s to 700 mm2/s at 50 °C. In the precision program, detector tubes and pumps from National Drager Inc. (see AnnexA1) were used for all samples having less than 2000 µmol/mol (ppm v/v) H2S while Mine Safety Appliances tubes and pumps were used for the one sample exceeding this concentration.
12.1.1 Repeatability - The difference between successive test results obtained by the same operator with the same apparatus under constant operating conditions on identical test material would, in the long run, in the normal and correct operation of the test method exceed the following value only in one case in twenty, where X = average of two test results:
repeatability = 0.20X + 10
12.1.2 Reproducibility - The difference between two single and independent test results obtained by different operators working in different laboratories on identical test material would, in the long run, exceed the following value only in one case in twenty, where X = average of the two results:
reproducibility = 0.30X + 15
12.2 Bias - Since there is no accepted reference material suitable for determining bias for the procedure in Test Method D5705 for measuring hydrogen sulfide, bias has not been determined. Furthermore, any bias in measurements made by using different length-of-stain detector tubes from different manufacturers is not known.
13. Keywords
13.1 hydrogen sulfide; length-of-stain detector tube; residual fuel oil
