25. Calculation
25.1 Calculate the percentage of phosphorus as follows:
Phosphorus, mass % = (P x 27.84)/W
where:
P = magnesium pyrophosphate, g, and
W = sample used, g.
26. Quality Control (QC)
26.1 Confirm the performance of the instrument of the test procedure by analyzing a QC sample (see 10.5, 15.5, and 22.11).
26.1.1 When QC/Quality Assurance (QA) protocols are already established in the testing facility, these may be used to confirm the reliability of the test result.
26.1.2 When there is no QC/QA protocol established in the testing facility, Appendix X1 can be used as the QC/QA system.
27. Precision and Bias
27.1 The precision of these test methods is not known to have been obtained in accordance with currently accepted guidelines.
27.2 The precision of these test methods as obtained by statistical examination of interlaboratory test results is as follows:
27.2.1 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 values only in one case in twenty:
27.2.2 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:
27.3 Bias - The bias of these test methods cannot be determined since an appropriate standard reference material containing a known level of phosphorus in liquid petroleum hydrocarbon is not available.
28. Keywords
28.1 additives; gravimetric; lubricating oils; phosphorus; photometric