ASTM D4715 Test Method for Coking Value of Tar and Pitch (Alcan)
10. Procedure
10.1 For greater accuracy, carry out the determination in duplicate.

10.2 Heat a clean porcelain crucible with its lid in the electric furnace, controlled at 550 more or less 10°C, for 2 h. After cooling to ambient temperature in a desiccator, weigh to the nearest 1 mg.

10.3 Weigh into the crucible, to the nearest 1 mg, a representative portion of 1 more or less 0.05 g of the test specimen. Place the wire support in the nickel crucible and make a bed 0.4 more or less 0.04 in. (10 more or less 1 mm) thick on the base of the crucible with the petroleum coke. Place the porcelain crucible containing the test portion in the wire support so that it sits on the bed of petroleum coke. Cover the porcelain crucible with its lid and completely fill the space between the two crucibles with the petroleum coke so that the porcelain crucible is completely embedded. Take care to avoid contamination of the sample by the coke. Cover the nickel crucible with its lid.

10.4 Place the prepared crucible on the crucible support and place the whole in the electric furnace controlled at 550 more or less 10°C, as quickly as possible, in order to avoid heat losses.
10.4.1 There should be a space of not less than 7 mm between the nickel crucible and the floor, walls, and roof of the furnace. The space between the crucible and the door, and the back wall of the furnace should not be less than 5 cm.

10.5 After 2.5 h, remove the nickel crucible from the furnace and allow to cool for 5 to 10 min. Lift the porcelain crucible out of the coke by means of the wire support, brush and wipe free from adhering coke powder, taking care to avoid contamination. Place the crucible and contents, covered, in a desiccator and allow to cool to ambient temperature. Weigh to the nearest 1 mg.

NOTE 1 - To clean the porcelain crucibles and lids, discard the residues and burn off carbonaceous matter by igniting at 700 to 1000°C in an electric furnace.

11. Calculation
11.1 Calculate the coking value of the sample as follows:
Coking value, mass % = 100A/B
where:
A = mass of residue, g, and
B = mass of sample, g.

11.1.1 If the determination was carried in duplicate, report the mean value.