ASTM D2533 Test Method for Vapor-Liquid Ratio of Spark-Ignition Engine Fuels
13. Report
13.1 Report the vapor-liquid ratio(s) to the nearest 0.1 unit and the corresponding temperature in degrees Fahrenheit or Celsius to 0.1°. Also report the pressure in millimetres of mercury if other than 760. If not reported, the pressure is understood to be 760 mm Hg.
13.2 If vapor-liquid ratios have been determined at a series of at least three temperatures, and if values at intermediate temperatures, or temperatures for intermediate V/L ratios are desired, proceed as follows: Plot the experimental results in the form of a curve of vapor-liquid ratio versus temperature, smoothing if necessary, on graph paper which can be read easily to 0.1 V/L and 0.2°F (or 0.1°C). Read from this curve the desired intermediate V/L and temperature values. Report V/L, temperature, and pressure as prescribed in 12.1, but accompany the result with the word "interpolated". Thus, for example, report "V/L = 15.0 interpolated at 127.6°F" or "V/L = 12.3 interpolated at 125.0°F and 665 mm Hg".
14. Precision and Bias
14.1 Precision - The precision of this test method for measuring the T (V/L = 20) value of gasoline and gasoline-oxygenate blends as determined by the statistical examination of interlaboratory test results10 is as follows:
14.1.1 Repeatability - The difference between two 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 values only in one case in twenty:
glycerol 1.0°C (1.8°F)
mercury 1.4°C (2.5°F)
14.1.2 Reproducibility - The difference between two single and independent results obtained by different operators working in different laboratories on identical test material would, in the long run, in the normal and correct operation of the test method, exceed the following values only in one case in twenty:
glycerol 1.3°C (2.3°F)
mercury 1.6°C (3.0°F)
14.2 Bias:
14.2.1 Absolute - Since there is no accepted reference material suitable for determining the bias for this test method, no statement on bias is being made.
14.2.2 Based on statistical analyses of the data from the 1991 cooperative testing program (see Note 20), the following relative bias statements were determined for T (V/L = 20):
14.2.2.1 Containing Fluids - No significant bias was determined between the methods using glycerol or mercury as the containing fluid with the gasolines without oxygenates.
14.2.2.2 Glycerol Containing Fluid - Using the mercury method as a standard, a small but significant bias of + 0.5°C (0.9°F) was found for the gasoline -15 V % MTBE blend data relative to the hydrocarbon-only gasoline data.
14.2.2.3 Test Methods - No significant bias was determined between this test method and Test Method D5188 data.
NOTE 21 - The precision and bias data were developed in a 1991 cooperative testing program based on the duplicate analysis of twelve gasolines and gasoline-oxygenate blends by a minimum of five laboratories. The test fuels had a range of oxygenate content (ethanol and MTBE) from 0 to 15 % by volume and a T (V/L = 20) range from approximately 37.8°C (100°F) to 60.0°C (140°F).
