ASTM D2318 Test Method for Quinoline-Insoluble (QI) 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 at 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 - A wet tar sample may either be dehydrated or used as received as long as conditions stated in 9.3.1 and 9.3.2 are met.
9.3.1 Dehydrate a representative portion of the bulk sample at atmospheric pressure using a simple side-arm 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.
9.3.2 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 mass percent, the QI content is corrected to a dry-tar basis (see 13.2). This alternative test 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 but will have a minimum of fine particles. 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, taking care to avoid excessive loss of volatile matter. 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 dry 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 Preservation of Samples - Store samples as large lumps or as solidified melts in closed containers. Discard working samples 24 h after crushing and sieving as changes in composition sometimes occur in pulverized pitch.
11. Crucible Preparations
11.1 If the crucible, after thorough cleaning (see 11.2), has been used for less than six determinations, clean it as follows: Remove the mat, wash the crucible with distilled water, dry, and ignite in a muffle furnace for 1 h at about 800 °C. Cool the crucible slowly by placing it in a drying oven for 1 h after removal from the furnace to prevent cracking and place it in a desiccator while still warm.
11.2 After the crucible has been used for six determinations, remove any residual ash from pores in the filtering area by boiling in 1 + 1 hydrochloric acid. Add equal volume of concentrated hydrochloric acid to distilled water. Then boil the crucible in distilled water, thoroughly back wash with distilled water, dry, and ignite as in 11.1.
