ASTM D974 – Acid and Base Number by Color-Indicator Titration
Many lubricants contain acidic or basic components. As the lubricant ages, the quantity of these components may change due to oxidation and degradation – typically acidic components increase and basic ones decrease. This test determines the acid number or base number of sample oil. Acid number is a measure of the quantity of acidic components, base number is measure of the quantity of basic components. This test is useful both for quality control of new oils and evaluation of service oils.
The sample is weighed into the titration vessel, titration solvent and indicator are added and the mixture is swirled. The resulting color determines if the acid number or the base number is to be determined. If the acid number is to be determined, the mixture is titrated with potassium hydroxide. If the base number is to be determined, the mixture is titrated with hydrochloric acid. The endpoint is determined at the color change. If the strong acid number is to be determined, boiling water is added to the sample, the water layer is extracted and titrated with potassium hydroxide. Reported is the acid number, strong acid number or the base number in mg KOH per gram of sample.
Sample size: 150 ml
- ASTM D664 – Acid Number, Potentiometric, 2001 or 2004 or 2009 or 2011A version
- ASTM D664 – Acid Number, Strong, 2001 or 2004 or 2009 or 2011A version
- ASTM D1093 – Acidity of Water Layer and distillation residues
- ASTM D1121 – Reserve Alkalinity of Antifreeze
- ASTM D2896 – Base Number – Perchloric Acid Method
- ASTM D2942 – Total Acid of Halogenated Organic Solvents
- ASTM D3242 – Acidity in Aviation Turbine Fuel
- ASTM D4739 – Base Number Total, by Hydrochloric Acid Method