ASTM D5188 Standard Test Method for Vapor-Liquid Ratio Temperature Determination of Fuels (Evacuated Chamber and Piston Based Method)
14. Report
14.1 Report T(V/L) temperature to the nearest 0.1 °C (0.2 °F) and the vapor-liquid ratio without reference to pressure.
14.2 If the sample was observed to be hazy in 12.5, report the test result as in 14.1, followed by the letter H.
NOTE 12 - The precision and bias statements have not been determined for hazy samples, since these types of samples have not been evaluated as part of an interlaboratory study.
NOTE 13 - The inclusion of the letter H in 14.2 is intended to alert the data recipient that the sample analyzed was hazy. In the event a laboratory has a computer system that is incapable of reporting alphanumeric results in accordance with the requirements in 14.2, it is permissible for the laboratory to report the result obtained as in 14.1, along with a statement or annotation that clearly conveys to the data recipient that the sample analyzed was hazy.
15. Precision and Bias
15.1 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 results is as follows:
15.1.1 Repeatability - The difference between two 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 ofthe test method exceed the following value only in one case in twenty:
0.6 °C (1.1 °F)
15.1.2 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, in the normal and correct operation of the test method exceed the following value only in one case in twenty:
0.9 °C (1.6 °F)
NOTE 14 - The precision data were developed in a 1991 cooperative testing program based on the duplicate analysis of twelve samples of 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).
15.2 Bias:
15.2.1 Absolute - Since there is no accepted reference material suitable for determining the bias for this test method, no statement on bias is being made.
15.2.2 Based on statistical analyses of the data from the 1991 cooperative testing program (see Note 14), the following relative bias statements were determined for T(V/L=20):
15.2.2.1 Test Method D5188 Test Instruments - No significant bias was determined between the data using the two test instruments.
15.2.2.2 V/L Test Methods - No significant bias was determined between the data determined using Test Methods D5188 and D2533, using mercury as the containing fluid.
15.2.3 A limited pilot study was conducted in 2011 using two single instruments for each technique, a V/L ratio of 20:1, and a sample set comprising 43 number of samples of mixtures of pure compounds and gasolines with T vl ranging from nominally 35 °C to 78 °C. Altough the minimum number of labs and sample requirements for a formal D6708 assessment was not met, the statistical evaluation methodology in D6708 was applied to comparison data from only two labs, with the outcome of no statistically observable bias between evacuated chamber technique and moveable piston technique. There was no statistically observable difference in repeatability performance. The reproducibility precision for the piston method has not been evaluated.
16. Keywords
16.1 gasoline; gasoline-oxygenate blends; petroleum products; T(V/L = 20) ; vapor-liquid ratio
