ASTM D2896 for base number of petroleum products
ASTM D2896 for base number of petroleum products by potentiometric perchloric acid titration
APPENDIXES
(Nonmandatory Information)
X1. TEST COVERAGE
X1.1 During the developments of the original test method (Procedure A) and the test method for the reduced titration solvent volume (Procedure B), cooperative testing was done on samples covering a wide range of types of oils, of additive concentrates which are used to prepare these oils, and of services for the oils. Even so, however, it was not possible to cover the complete range of base numbers. It is believed that reasonable interpolation and extrapolation from the ranges used will not introduce serious errors in the precision.

X1.2 The ranges used for the precision were as follows:
X1.2.1 Fresh Oils - Base numbers from 6 to 70.

X1.2.2 Additive Concentrates - Base numbers from 5 to 300.

X1.2.3 Used Oils on Which Were Employed the Forward Titration - Base numbers from 5 to 27.

X2. ALTERNATIVE SOLVENT
X2.1 In order to eliminate the chlorobenzene from this test method, an alternative solvent was developed. Cooperative testing was done on samples covering a wide range of types of oils, both new and used, and of additive concentrates used to prepare these oils. Results have shown that the two solvents provide statistically equivalent results; however, the precision of the alternative solvent is worse than the original. Paragraph X2.5.5 describes how to compare results using the two different solvents.

X2.2 Reagents
X2.2.1 Xylenes, mixed. (Warning - Flammable. Vapor harmful.)

X2.2.2 Alternative Titration Solvent - Add one volume of glacial acetic acid to two volumes of mixed xylenes.

X2.3 Procedure
X2.3.1 Procedure A of this test method is followed exactly, except that mixed xylenes replace chlorobenzene and the alternative titration solvent replaces the titration solvent.

NOTE X2.1 - The addition of approximately 10 % acetone by volume to the alternative titration solvent has been shown to reduce electrode noise and may be used. However, the test method precision using the acetone addition to the alternative titration solvent has not been determined.

X2.4 Report
X2.4.1 Report the result as follows:
Base Number (Test Method D2896 - Alternative Solvent, X2) = Result

X2.5 Precision and Bias
X2.5.1 The precision and bias of this alternative solvent test method was determined through a round robin using new and used oils as well as additive concentrates. The base number values covered a range from approximately 0.5 to 400. Statistical analysis of round robin results are available in the research report.

X2.5.2 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:
6.2 % of the mean

NOTE X2.2 - As part of the same round robin, these samples were analyzed using chlorobenzene. The repeatability using chlorobenzene was calculated to be 3.4 % of the mean.

X2.5.3 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:
16.2 % of the mean

NOTE X2.3 - As part of the same round robin, the same samples were analyzed using chlorobenzene. The reproducibility using chlorobenzene was calculated to be 8.7 % of the mean.

X2.5.4 Relative Bias - No systematic bias was detected between the chlorobenzene and mixed xylenes methods.

X2.5.5 To compare results obtained using different solvents, use the following:
X2.5.5.1 Repeatability - The difference between two test results using the two different solvent systems, 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:
5.0 % of the mean

X2.5.5.2 Reproducibility - The difference between two single and independent results using the two different solvent systems, 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:
13.0 % of the mean

X3. ALTERNATIVE ELECTROLYTES
X3.1 The use of alternative electrolytes has been studied in certain laboratories. Limited data on various types of oils and additives have shown that the two alternative electrolytes studied provide statistically equivalent data as sodium perchlorate in glacial acetic acid.

X3.2 Reagents
X3.2.1 Tetraethylammonium Bromide (TEABr).

X3.2.2 Ethylene Glycol.

X3.2.3 Tetraethylammonium Bromide Electrolyte - Prepare a 0.4 M solution of TEABr in ethylene glycol.

X3.2.4 Ethanol. (Warning - Flammable and toxic, especially when denatured.)

X3.2.5 Lithium Chloride, LiCl.

X3.2.6 Lithium Chloride Electrolyte - Prepare a 1 M–3 M solution of lithium chloride (LiCl) in ethanol.

X3.3 Procedure
X3.3.1 Procedures A and B of this test method are followed exactly, except LiCl in ethanol or TEABr in ethylene glycol replaces NaClO4 in acetic acid as the electrolyte in the reference electrode.

X3.4 Report
X3.4.1 Report the result as follows:
Base Number (Test Method D2896 - Alternative Electrolyte, X3) = Result

X3.5 Precision and Bias
X3.5.1 The precision and bias of these alternative electrolytes are not established. Preliminary data shows good correlation when compared to the data obtained from the perchlorate electrolyte specified in this test method.

X4. CHECK FOR ELECTRODE PERFORMANCE
X4.1 The kinetic electrode test measures the kinetic response of the electrode. Electrodes can calibrate with acceptable slope and intercept values yet still not have a response good enough for titration. The speed of response and subsequent stability is important for a titration electrode. A manual method is described below which can be carried out with a pH meter or titrator set to read millivolts continuously.

X4.2 The essence of the method is to challenge the electrode coming from rest in a water solution with buffers and measure the potential after 30 and 60 s. A fast electrode reaches a stable point in less than 30 s and changes little from 30 to 60 s. Use buffers pH 4, pH 7, and pH 11 for this check as needed.

X4.3 The procedure for carrying out the test is as follows. Set the titrator or pH meter to read millivolts continuously. Have provision for stirring the buffer solution at the same speed used for the titrations. Allow the electrode to stabilize for one minute in distilled or equivalent deionized water. Remove the electrodes from the water and place them in the pH 4 buffer, starting a stop watch at about the moment when the buffer touches the electrode. After 30 s, note the potential. After another 30 s, note the potential again. The difference between the two potentials is termed the drift. Repeat the procedure for pH 7 buffer and pH 11 buffer.

X4.4 Calculate the drift for each of the three buffers. The electrode response may be judges as follows:
(1) drift < 1, excellent
(2) 1 < drift < 2, good
(3) 2 < drift < 3, acceptable
(4) 3 < drift < 4, questionable
(5) 4 > drift, unacceptable

X4.5 The difference between the 60-second potentials for pH 4 buffer and pH 7 buffer should be greater than 162 mV, or 54 mV/pH number. Electrodes with a slope less than 54 mV/pH number are not reliable for titration.

SUMMARY OF CHANGES
Subcommittee D02.06 has identified the location of selected changes to this standard since the last issue, D2896-07, that may impact the use of this standard. (Approved July 15, 2007.)
(1) Revised 6.3.
(2) Removed "calomel" and replaced with "reference" electrode throughout.
(3) Added new 19.1 and renumbered subsequent sections.
(4) Added Table 1.
(5) Added Footnote 7.

Subcommittee D02.06 has identified the location of selected changes to this standard since the last issue, D2896-06, that may impact the use of this standard. (Approved Jan.15, 2007.)
(1) Clarified the requirements for quality of water to be used in 7.2.
(2) Added a new non-mandatory Appendix X3 for using alternative electrolytes