ASTM D2415 Standard Test Method for Ash in Coal Tar and Pitch
5. Apparatus
5.1 Muffle Furnace - A muffle furnace with good air circulation and capable of having its temperature regulated at 900 °C +/- 10 °C.
5.2 Dish or Crucible, porcelain, silica, or platinum, having a capacity of 35 mL to 45 mL and a diameter at the top of 55 mm to 60 mm.
5.3 Sieve, U.S. Standard 600 µm (No. 30), conforming to Specification E11.
6. Bulk Sampling
6.1 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.
7. Dehydration of Sample
7.1 Hard Pitch - If the solid bulk sample contains free water, air-dry a representative portion in a forced draft oven at 50 °C.
7.2 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.
7.3 Tar - Dehydrate a representative portion of the bulk sample in accordance with Test Method D850, but stop the distillation when the temperature reaches 170 °C. Separate any oil from the water which 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.
8. Preparation of Working Sample
8.1 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 600 µm (No. 30) sieve.
8.2 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.
8.3 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.
8.4 Preservation of Samples - Store samples as large lumps or as solidified melts in closed containers. Do not save crushed samples for future analyses since changes in composition sometimes occur in pulverized pitch.
