ASTM D1093 for Acidity of Hydrocarbon Liquids and Their Distillation Residues
4. Summary of Test Method
4.1 The sample of distillation residue or hydrocarbon liquid is shaken with water and the aqueous layer tested for acidity to methyl orange indicator.
4.2 The aqueous layer can also be tested for basicity using phenolphthalein indicator.
5. Significance and Use
5.1 Some petroleum products are treated with mineral acid as part of the refining procedure. Obviously, any residual mineral acid in a petroleum product is undesirable. The absence of a positive indication in the test for acidity of the distillation residue or aqueous extract of a hydrocarbon liquid is an assurance of the care used in refining the fuel or solvent.
