9. Calculation and Report
9.1 Read the volume of the solid sediment at the bottom of each centrifuge tube, estimating to 0.1 mL or closer if possible. If the two readings differ by not more than 0.1 mL, report the mean of the two as the ASTM Precipitation Number. If the two readings differ by more than 0.1 mL, make two more determinations and report the average of the four determinations.
10. Precision and Bias
10.1 The precision of this test method as determined by statistical examination of interlaboratory results is as follows:
10.2 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:
10.3 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:
10.4 Bias - This procedure is empirical, precipitation number is defined solely by this procedure, therefore, no statement of bias can be made.
11. Keywords
11.1 asphaltenes; lubricating oils; precipitation number