ASTM D473 test method for sediment in crude oils and fuel oils
ASTM D473 standard test method for sediment in crude oils and fuel oils by the extraction method
8. Procedure
8.1 For referee tests, use a new extraction thimble (5.1.1.3) prepared in accordance with 8.2. For routine tests, thimbles may be reused. When reusing thimbles, the extraction to constant mass for one determination should be considered as the preliminary extraction for the succeeding determination. After several determinations (the accumulated sediment may be sufficient to interfere with further determinations), follow the procedure described in 8.3 to remove the combustible portion of the accumulated sediment. Avoid excessive reuse of thimbles, as over time the pores become clogged with inorganic material resulting in falsely high results. When in doubt regarding a higher than normal result, discard the thimble and retest using a new thimble.
8.2 Preparation of a New Thimble - Rub the outside surface with fine sandpaper and remove all loosened material with a stiff brush. Give the thimble a preliminary extraction with the toluene, allowing the solvent to drip from the thimble for at least 1 h. Then dry the thimble for 1 h at a temperature of 115 to 120°C (240 to 250°F); cool in a cooling vessel, for 1 h, and weigh to the nearest 0.1 mg. Repeat the extraction until the masses of the thimble after two successive extractions do not differ by more than 0.2 mg.
8.3 Preparation of a Used Thimble - Remove the combustible portion of the accumulated sediment by heating the thimble to a dull red heat for 20 min (preferably in an electric furnace maintained at approximately 750°C (1380°F)). Subject the thimble to a preliminary extraction as described in 8.2 before using it for another determination.
8.4 Place an estimated 10-g test portion of the sample in the thimble immediately after the sample has been mixed. Do not attempt to adjust this estimated 10-g portion to any exact predetermined amount. Weigh the thimble plus test portion to the nearest 0.01 g. Add 150 mL to 200 mL of toluene to the flask. Place the thimble in the extraction apparatus, place on the heat source, and extract with the hot toluene for 30 min after the solvent dripping from the thimble becomes colorless. Ensure that the rate of extraction is such that the surface of the mixture of oil and toluene in the thimble does not rise higher than to within 20 mm of the top.
8.5 When testing samples determined to have a water content greater than 10 % volume, use the assembly shown in Fig. 1, Apparatus B. In this procedure, remove any water in the test portion as its toluene azeotrope and is collected in the water cup, where it separates as a bottom layer. The toluene layer overflows into the thimble. If the cup becomes full of water, allow the apparatus to cool and empty the cup.
8.6 After the extraction is completed, dry the thimble for 1 h at 115 to 120°C (240 to 250°F) in the oven; cool in the cooling vessel, for 1 h; and weigh to the nearest 0.1 mg.
8.7 Repeat the extraction, allowing the solvent to drip from the thimble for at least 1 h but not longer than 1.25 h; dry, cool, and weigh the thimble as described in 8.6. Repeat this extraction for further 1-h periods, if necessary, until the masses of the dried thimble plus sediment after two successive extractions do not differ by more than 0.2 mg.
9. Calculation
9.1 Calculate the sediment content of the sample as a percentage by mass of the original sample.
where:
S = sediment content of the sample as a percentage by mass,
m1 = mass, of the thimble, g,
m2 = mass, of the thimble plus test portion, g, and
m3 = mass of the thimble plus sediment, g.