ASTM D5984 Test Method for Semi-Quantitative Field Test Method for Base Number
ASTM D5984 Standard Test Method for Semi-Quantitative Field Test Method for Base Number in New and Used Lubricants by Color-Indicator Titration
4. Summary of Test Method
4.1 To determine the base number of an oil sample, the sample is dissolved in a fixed amount of isooctane and alcoholic hydrochloric acid. The solution is mixed well with 7 mL of sodium chloride solution and the aqueous and organic phases are allowed to separate. The aqueous phase is then decanted off and a small amount of methyl red indicator is added. The solution is titrated with a solution of sodium hydroxide contained in a calibrated 1 mL micro-burette. When the solution changes from magenta to yellow, the titration is stopped and the base number is read off the side of the titration burette.
5. Significance and Use
5.1 New and used petroleum products can contain basic constituents that are present as additives or as degradation products formed during service. The amount of these additives in an oil can be determined by titrating against an acid. The base number is a measure of the amount of basic substance in the oil, always under the conditions of the test. A decrease in base number is often used as a measure of lubricant degradation, but any condemning limits must be empirically established.
5.2 This test method uses reagents that are considered less hazardous than most reagents used in alternate base number methods. It uses pre-packaged reagents to facilitate base number determinations in the field where scientific equipment is unavailable and quick results are at a premium.
NOTE 1 - Results obtained by this test method are similar to those obtained by Test Method D2896.
