ASTM D2158 Standard Test Method for Residues in Liquefied Petroleum (LP) Gases
10. Preparation of Apparatus
10.1 Wash all glassware that is to be used in the test in the selected solvent.
10.2 Verification of cleanliness of glassware and solvent.
10.2.1 Add 10 mL of a new sample of solvent to the centrifuge tube.
10.2.2 Mark the center of the filter paper with a pencil or other non-pentane-soluble writing tool.
10.2.3 Fill the syringe or equivalent liquid dispensing device (see 7.3) with a portion of the solvent drawn from the centrifuge tube and direct 0.1-mL portions of the solvent to the mark on the paper.
10.2.3.1 The solvent is added in 0.1-mL increments to confine the solvent ring to a circle about 30 to 35 mm in diameter. The filter paper should be held level during the solvent addition. One method is to place it on a 250-mL beaker.
10.2.4 Allow the solvent to evaporate for 2 min, and note the persistence of an oil ring.
10.2.4.1 The presence of an oil ring shall be observed by holding the dry filter paper between the eye and a bright incandescent light or strong daylight.
10.2.4.2 If no oil ring appears after 1.5 mL of solvent has been added, the solvent and glassware are satisfactory.
10.2.4.3 The appearance of an oil ring indicates either improperly cleaned glassware or contaminated solvent.
