ISO 3735 Crude petroleum and fuel oils - Determination of sediment - Extraction method
8 Procedure
8.1 Place a test portion of approximately 10 g in the thimble (5.1.3) immediately after the laboratory sample has been mixed. Do not attempt to adjust the estimated 10 g portion to any exact predetermined mass.
Weigh the thimble plus test portion to the nearest 0.01 g. Add 150 ml to 200 ml of toluene (4.1) to the flask, place the thimble in the extraction apparatus (5.1), place on the heater (5.1.6) and extract with hot toluene for 30 min after the solvent dripping from the thimble becomes colourless.
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 20 mm of the top.
8.2 When the water content of the sample is known or suspected to be above 10 % (V/V), use the assembly illustrated in figure 1 b).
NOTE In this procedure, any water in the test portion is removed as its toluene azeotrope and collects 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.
8.3 After the extraction is completed, dry the thimble for 1 h in the oven (5.4), cool for 1 h in the cooling vessel (5.5), and weigh to the nearest 0.1 mg.
8.4 Repeat the extraction, allowing the solvent to drip from the thimble for at least 1 h but not longer than 1 h 15 min. Then dry, cool and weigh the thimble as described in 8.3. 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
Calculate the sediment content of the sample, S, as a percentage by mass, using the equation:
S = (m3 - m1)/(m2 - m1) x 100
where
m1 is the mass, in grams, of the thimble;
m2 is the mass, in grams, of the thimble plus test portion;
m3 is the mass, in grams, of the thimble plus sediment.
