ASTM D5770 Test Method for Semiquantitative Micro Determination of Acid Number of Lubricating Oils During Oxidation Testing
8. Procedure
8.1 Sampling - Withdraw the minimal amount of the test oil from the oxidation test cell according to the procedure specified in the oxidation test method.
NOTE 4 - As oxidized oils can change appreciably in storage, samples should be tested as soon as possible after removal from the oxidation test equipment.
8.2 Using the syringe, measure 2.0 mL of the titration solution into a 10 mL beaker or vial.
8.3 Using the dropping pipet, add the oil sample to the titration solution one drop at a time, swirling constantly.
8.4 Count the number of drops of oil sample required to change the titration solution color from blue-green to orange. Consider the titration complete when the orange color is stable for a minimum of 10 s.
8.5 Repeat 8.2 through 8.4 using the acid number reference solution in place of the oil sample as the titrant of 2.0 mL of titration solution, so that the final colors for the two beakers match.
