ASTM D3339 Test Method for Acid Number of Petroleum Products
ASTM D3339 Standard Test Method for Acid Number of Petroleum Products by Semi-Micro Color Indicator Titration
11. Report
11.1 Report the result as follows:
Acid Number, (Test Method D3339) = (Result)

12. Quality Control Checks
12.1 Confirm the performance of the test procedure by analyzing a quality control (QC) sample that is, if possible, representative of the samples typically analyzed.

12.2 Prior to monitoring the measurement process, the user of the method needs to determine the average value and control limits of the QC sample.

12.3 Record the QC results and analyze by control charts or other statistically equivalent technique to ascertain the statistical control status of the total testing process. Any out-of-control data should trigger investigation for root cause(s). The results of this investigation may, but not necessarily, result in instrument recalibration.

12.4 The frequency of QC testing is dependent on the criticality of the quality being measured, the demonstrated stability of the testing process, and customer requirements. Generally, a QC sample should be analyzed each testing day. The QC frequency should be increased if a large number of samples are routinely analyzed. However, when it is demonstrated that the testing is under statistical control, the QC testing frequency may be reduced. The QC precision should be periodically checked against the precision listed in the Precision and Bias Section of this method to ensure data quality.

12.5 It is recommended that, if possible, the type of QC sample that is regularly tested be representative of the sample routinely analyzed. An ample supply of QC sample material should be available for the intended period of use, and must be homogeneous and stable under the anticipated storage conditions. Because the acid number can vary while an out-of-control situation arises, the stability of the QC sample can be a source of the error.

13. Precision and Bias
13.1 This precision section applies only to new and used petroleum-based, inhibited steam turbine and hydraulic oils. Insufficient data are available on other oils coming within the scope of this test method so no precision is given for such oils.

13.2 The precision of this test method as determined by statistical examination of interlaboratory results is as follows:
13.2.1 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 this test method, exceed the following values only in one case in twenty:

where:
X = mean acid number of sample.

13.2.2 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 this test method, exceed the following values only in one case in twenty:

where:
X = mean acid number of sample.

13.3 Bias - The procedure in this test method has no bias because the value of the acid number can be defined only in terms of this test method.

14. Keywords
14.1 acid number; petroleum products; semi-micro color indicator titration