ASTM D4072 Standard Test Method for Toluene-Insoluble (TI) Content of Tar and Pitch
12. Procedure
12.1 The mass of sample taken for analysis shall yield between 150 mg and 250 mg of matter insoluble in toluene (TI), unless this would require less than the minimum acceptable sample mass of 1 g, in which case 1 g shall be used.
12.2 Place the required amount of sample in a tared 150 mL beaker and weigh to the nearest 0.5 mg. Pour 60 mL of toluene into the beaker, stirring continuously while introducing the toluene, to ensure complete mixture of the sample and toluene and thorough dispersion of the insoluble matter (see 7.1). Place the beaker on an electric hot plate or on a steam or water bath and heat the contents to a temperature of 95 °C +/- 5 °C. Maintain this temperature for 25 min. Stir occasionally with a stirring rod during this period to ensure that the sample is completely dispersed in the toluene. Check for completeness of dispersion by inspecting the bottom of the beaker for undigested material.
12.3 Place the tared extraction thimble in a filter tube supported over a beaker or flask. Wet the thimble completely with toluene. After digestion, carefully decant portions of the hot mixture into the wetted thimble (see 7.1). Do not permit the level of the toluene to rise higher than 20 mm from the top of the thimble. It is advisable while filtering to retain the major part of the insoluble matter in the beaker. Finally transfer the insoluble matter from the beaker to the thimble with small portions of toluene. Wash the beaker with toluene until it is clean, using a suitable brush or policeman to detach any particles adhering to the beaker. Transfer all washings to the thimble.
12.4 When almost all toluene has drained from the thimble, wash the thimble and its contents once with a small quantity of toluene. Allow the toluene to drain from the thimble.
12.5 While the extraction thimble is still moist with toluene, remove it from the filter tube and place it in the wire support of the extraction apparatus. Cover the thimble with the paper cone, point down. Assemble the extraction apparatus on a hot plate, with a felt gasket between the top of the extraction flask and condenser cover, and with fresh toluene in the bottom of the extraction flask. Add three to six small lumps of pumice stone to the flask to promote smooth boiling, thereby preventing bumping and spattering during extraction. The surface of the toluene in the flask shall be about 25 mm below the bottom of the thimble (see 7.1).
12.6 Conduct the extraction at such a rate of heating that condensed toluene falls continuously from the condenser at a rate of not less than 1 nor more than 2 drops/s. Continue the extraction at this rate for a period of 18 h (Note 1).
NOTE 1 - The reflux rate can be affected by the ambient temperature, especially when the apparatus is operating overnight unattended (for example, the temperature of the laboratory is reduced at night and the reflux rate slows or ceases). One way to alleviate this condition is to place a metal shield around the heater and extraction apparatus which would prevent the colder air entering the hood from excessively cooling the extraction apparatus. The shield can be as simple as a can with the ends cut out.
12.7 At the end of this period, remove the heat source and allow the toluene to drain from the thimble, then remove the thimble from the extraction apparatus. Remove the paper cone and gently lay the thimble on its side, with the open end tilted up, on a watch glass in the fume hood so that the toluene can evaporate. Leave it for 30 min. Place the air-dried thimble in a drying oven at 105 °C +/- 5 °C for 60 min. Remove the dry thimble from the oven and place it immediately in a desiccator. When cool, weigh the thimble and contents to the nearest 0.5 mg, and record the mass (see 12.8).
12.8 If the mass of matter insoluble in toluene is less than 150 mg or more than 250 mg, repeat the determination with an adjusted sample weight of not less than 1 g (see 11.1).
