ASTM D1093 for Acidity of Hydrocarbon Liquids and Their Distillation Residues
9. Procedure
9.1 All distillation flasks and glassware used in this test shall be clean and dry There shall be no contaminant present that could affect the acidic or basic nature of the material under test.
9.2 Distillation Residue - Cool the residue from the distillation (obtained by using Test Method D86, Method D850, or Test Method D1078 and drain immediately into a test tube. Add a volume of water equal to about three times the volume of residue, stopper, and shake the tube vigorously for 30 s. Allow the liquids to separate and pipet the clean aqueous layer into a second clean test tube. Add 1 drop of methyl orange indicator solution and observe the color.
9.3 Hydrocarbon Liquid - Place 50 mL of the sample, 15 mL of water, and 3 drops of methyl orange indicator solution in a clean centrifuge tube. Stopper the tube with a clean stopper (Caution, see Note 4), shake vigorously for 30 s, and centrifuge at 1500 rpm for 10 min. Remove the centrifuge tube and observe the color of the aqueous layer.
NOTE 4 - Caution: During shaking, vent the centrifuge tube at frequent intervals, especially at the initial 5 s of shaking so that any build-up of vapors or pressure can be released.
9.4 For the determination of basicity use 3 drops of phenol-phthalein indicator instead of methyl orange in either 9.2 or 9.3.
