12. Procedure
12.1 Place not less than 5 g of the prepared crushed or lump sample in the dry, tared pycnometer and weigh with the stopper to the nearest 0.5 mg. Record the mass. Cover the pitch to a depth of about 10 mm with freshly boiled distilled water cooled to a temperature of about 20 °C. Add several drops of a stock solution of Aerosol OT containing 0.1 g/mL of solution or other wetting agent.
12.2 Place the unstoppered pycnometer in the vacuum desiccator and evacuate the air at such a rate that no sudden or violent ebullition occurs. Maintain a pressure in the desiccator of 2.7 kPa to 3.3 kPa (20 torr to 25 torr), as measured by the manometer, for at least 15 min to remove all entrapped air bubbles. If air bubbles persist, add more wetting agent and continue the process until no air bubbles are visible.
12.3 Remove the pycnometer from the desiccator and fill with freshly boiled distilled water that has been cooled to about 20 °C. Insert the stopper with a rotary motion to secure a firm seat, making sure that no air is entrapped. Then completely immerse the pycnometer in the water bath at 25 °C for a minimum of 30 min.
12.4 After 30 min, raise the pycnometer until the top of the stopper is above the water level, then quickly and carefully wipe the water off the flat surface of the stopper, taking care not to remove water from the capillary tube. Remove the pycnometer from the bath and dry with a clean, dry cloth or with soft, absorbent paper. Weigh immediately to the nearest 0.5 mg and record the mass.
13. Calculation
13.1 Calculate the relative density of the pitch as follows:
sp gr = (W3 - W1)/[(W2 - W1) - (W4 - W3)] = W/[W - (W4 - W2)]
where:
W = mass of sample (W3 - W1),
W1 = mass of pycnometer,
W2 = mass of pycnometer filled with water at 25 °C,
W3 = mass of pycnometer with sample, and
W4 = mass of pycnometer with sample filled with water at 25 °C.
13.2 Calculate the density of the pitch as follows:
Density = relative density x WT
where:
relative density = calculation from 13.1, and
WT = density of water at test temperature in desired units.
