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
8. Procedure
8.1 Obtain samples for analysis by this test method in accordance with instructions given in Practice D4057 or D4177.
8.2 If a sample is to be taken directly from a hot engine, follow the manufacturer's instructions for obtaining a representative sample. Allow the oil to cool to <50°C before proceeding further.
8.3 It is essential to ensure the sample is representative since any sediment can be acidic or basic or have adsorbed acidic or basic material from the sample. When necessary, samples are warmed to aid mixing. Used oils should be vigorously mixed to ensure homogeneity before sampling.
8.4 As used oils can change appreciably in storage, samples shall be tested as soon as possible after removal from the lubricating system.
8.5 Prepare the oil sample by shaking well to disperse any particulates.
8.6 Place the tip of the fixed volume sampling syringe into the oil sample. Draw back the plunger of the sampling syringe until it stops. Remove the syringe from the oil sample and wipe the outside clean of any excess oil. Dispense the entire volume of the syringe into the first test tube. Replace the cap on the test tube.
8.7 Add 1.0 mL of 2,2,4-trimethyl pentane (isooctane) and shake the tube well to mix the oil with the diluent. Add 1.0 mL of 0.114 mol/L alcoholic HCl and shake the tube well for 30 s, allowing the acid to react with the diluted oil sample.
8.8 Pour 7.0 mL 20 % NaCl solution into the oil mixture. Cap the tube and shake the mixture well for 30 s so that the two phases are completely dispersed. Stand the tube upside-down on its cap and allow the aqueous and organic phases to separate.
8.9 Place the plastic filter into the top of the second test tube. Keeping the first test tube upside-down and vertical, open the dispenser cap on the tube and dispense exactly 5 mL of the aqueous solution through the filter into the second test tube. Stop dispensing as soon as 5 mL has been placed in the tube.
8.10 Place the 1.0 mL micro-burette into the tube containing the 5.0 mL of aqueous extract. Seal the burette into place by screwing the threaded cap of the burette onto the test tube. Add 0.5 mL of the methyl red indicator solution and disperse the indicator throughout the solution by gently shaking. Start slowly dispensing the titrant into the solution and shake gently. As soon as the solution turns from magenta to yellow, stop the titration and read the result, in base number units, off the side of the burette barrel. The reading should be taken at the tip of the plunger.
