12. Procedure
12.1 Weigh 0.50 g sample to the nearest 0.5 mg in a 150 mL tared beaker.
12.2 While stirring sample with a glass rod, add 75 mL of hot toluene (95 °C +/- 5 °C) and continue stirring for a few minutes until the sample is dispersed. Digest sample containing toluene on an appropriate heat source (preferably a hot water or steam bath) at 95 °C +/- 5 °C for 25 min with occasional stirring.
12.3 While sample is digesting, weigh the alundum thimble, AN 485 (formerly RA 98, 20 µm porosity, 30 mm by 80 mm size) to nearest 0.5 mg. Place the thimble in a filtering tube, which is supported on a funnel rack or equivalent apparatus to drain soluble portion of sample.
12.4 Pour the digested sample into the thimble. Avoid filling the thimble higher than 20 mm from the top. Use a glass rod, a brush, or a rubber policeman, if necessary, and cold toluene from a wash bottle to completely transfer the insoluble particles into the thimble.
12.5 When most of the solution has drained from the thimble, transfer the thimble to the extraction apparatus as described in Test Method D4072. With a beaker, add hot toluene to extraction flask. Fill to a level approximately 25 mm below the bottom of thimble.
12.6 Adjust the hot plate, and set the drip (reflux) rate of toluene at 120 drops/min to 150 drops/min from the condenser to maintain the level of liquid in the thimble. Continue extraction for 3 h. The liquid level is easily observed if the paper cone is replaced with one made from coarse stainless steel or brass screen. However, it is not necessary to use a cone.
NOTE 1 - One could fill extraction flask to required level, turn heat on before thimble is placed into basket.
12.7 Cut heat off, let drain, remove with tongs, and place thimble in filtering tube. Wash the inside and outside ofthimble with acetone several times from a wash bottle, starting from top of thimble (several small washes are more efficient than filling the thimble). Place thimble in an oven at 110 °C +/- 5 °C for 30 min. Cool in a desiccator and weigh.
13. Calculation
13.1 Calculate the toluene-insoluble (TI) content as follows:
TI, mass% = 100 (B - A)/C
where:
A = mass of the alundum thimble,
B = mass of alundum thimble plus toluene-insolubles, and
C = mass of sample.
13.2 If the TI was determined on a wet tar sample (see 9.3.1), correct the TI value determined in 13.1 to a dry-tar basis as follows:
