ASTM D4072 Standard Test Method for Toluene-Insoluble (TI) Content of Tar and Pitch
8. Bulk Sampling
8.1 Samples from shipments shall be taken in accordance with Practice D4296, and shall be free of foreign substances. Thoroughly mix the sample immediately before removing a representative portion for the determination or for dehydration.
9. Dehydration of Sample
9.1 Hard Pitch - If the solid bulk sample contains free water, air-dry a representative portion in a forced draft oven at 50 °C.
9.2 Soft Pitch - If the presence of water is indicated by surface foam on heating, maintain a representative portion of the bulk sample of a temperature between 125 °C and 150 °C in an open container until the surface is free of foam. Take care not to overheat, and remove heat source immediately when foam subsides.
9.3 Tar - Dehydrate a representative portion of the bulk sample at atmospheric pressure using a simple sidearm distillation apparatus similar to the one in Test Method D850 and stop the distillation when the temperature reaches 170 °C. Separate any oil from the water that has distilled over (if crystals are present, warm sufficiently to ensure their solution) and thoroughly mix the oil with the residual tar in the still after the latter has cooled to a moderate temperature.
9.3.1 As an alternative to dehydration, the water content of the tar is determined by Test Method D95 and, if the water content is less than 10 % by mass, the TI content is corrected to a dry-tar basis (see 13.2). This alternative method applies only to stable emulsions of water in tar, that is, no water separates when the tar sample is left undisturbed for 24 h at room temperature.
10. Preparation of Working Sample
10.1 Hard Pitch - If the pitch can be crushed at room temperature, prepare a 20 g working sample by suitable crushing, mixing, and quartering of a representative portion of the dry sample. The crushing can be done with a small jaw crusher and a mullite mortar and pestle. No particle in the representative sample shall be larger than 5 mm in any dimension. Crush this sample so that all of it will pass the 250 µm (No. 60) sieve. Store the sieved working sample in a tightly closed container and use within 24 h (see 10.4).
10.2 Soft Pitch - If the pitch is too soft to grind and too sticky to mix, heat a representative portion of the dry sample to the lowest temperature that will permit passage through the 600 µm (No. 30) sieve. Do not exceed 10 min for this melting period. Pass the heated sample through the 600 µm sieve to remove foreign matter.
10.3 Tar - Heat a representative portion of the tar to the lowest temperature that will permit passage through the 600 µm (No. 30) sieve: then filter through this sieve to remove foreign matter.
10.4 Discard working samples 24 h after crushing and sieving as changes in composition sometimes occur in pulverized pitch.
11. Preparation of Extraction Thimble
11.1 Dry the clean thimble in an oven at 105 °C +/- 5 °C for 45 min, cool in a desiccator, and weigh to the nearest 0.5 mg. Record the mass.
11.1.1 After each use, ignite the thimble at 700 °C to 800 °C for a few hours. Cool the thimble slowly by placing in a drying oven for 1 h after removal from the furnace to prevent cracking. Before reuse, condition the thimble as described in 11.1.
11.1.2 After repeated use, boil the thimble in 1 + 1 hydrochloric acid. (Add equal volume of concentrated hydrochloric acid to distilled water.) to remove residual ash from the pores. Then boil the thimble in distilled water and wash with water. After drying at 105 °C, ignite and condition the thimble as described in 11.1 and 11.1.1.
