ASTM D1480 Test Method for Density and Relative Density (Specific Gravity) of Viscous Materials by Bingham Pycnometer
10. Procedure for Viscous Liquids
10.1 Weigh the pycnometer as directed in Section 8.
10.2 Warm, in an oven or convenient warming chamber, the pycnometer, syringe with needle, and sample to a convenient working temperature consistent with the fluidity and volatility of sample. Draw the requisite amount of sample into the syringe and immediately fill the warmed pycnometer taking care to avoid occluding air bubbles in the pycnometer bulb or capillary. Continue the addition of sample, withdrawing the filling needle gradually so that the tip remains immersed in the sample, until the sample has been added to a depth of 10 or 20 mm in the expansion chamber above the capillary, depending upon the amount of contraction expected.
10.3 Immerse the pycnometer bulb in the constant-temperature bath. As the sample contracts continue sample addition before the level recedes into the capillary or until a sufficient amount has been added to maintain the meniscus slightly above the calibration mark at the reference temperature. Allow to equilibrate to reference temperature.
NOTE 9 - Equilibration time depends upon the viscosity and temperature of the sample at the time of filling. Usually this is three to four times that required for a fluid sample. A safe criterion is to allow 15 min more equilibration time after the meniscus remains stationary.
10.4 Remove excess sample with the 16-gage needle attached to a vacuum line, warming the needle if necessary. Swab the capillary above the calibration mark and the overflow chamber several times with a pipe cleaner or small cotton swab slightly moistened with a suitable solvent. Follow with a dry swab. Final adjustment to the mark may be done by picking out sample with a small probe, splinter, or wire.
10.5 Remove the pycnometer from the bath, wash the outer surface with a suitable solvent followed by acetone and dry thoroughly with a clean, lint-free, slightly damp cloth. Observe the same cleaning procedure as used in calibrating the pycnometer in the bath. Allow the pycnometer to come to room temperature and weigh to the nearest 0.1 mg.
11. Procedure for Melted Solids at High Temperature
11.1 Place the sample in a heat-resistant container and bring to a temperature 8 to 12°C above its melting point in an explosion-proof oven.
11.2 Insert the pycnometer, previously weighed to the nearest 0.1 mg, in the lower chamber of the thermal shield and lightly clamp the syringe in the upper chamber so that the filling needle is inside the pycnometer. Apply power to the shields until the temperature is 2 to 3°C above the melting point of the sample, then reduce the voltage until the shield temperature increases less than 0.5°C/min.
NOTE 10 - In the absence of a thermal shield, an oven can be fitted with a rack to support the pycnometer and hypodermic, and the whole operation of charging the syringe and filling the pycnometer performed in the oven. Weights applied to the syringe plunger reduce the filling time. An internal light and glass door for the oven are aids in this procedure.
11.3 After thermal equilibrium of sample, pycnometer, and syringe has been established, raise the upper shield, swing to one side, and quickly charge the syringe.
11.4 Quickly wipe the needle, swing the syringe over, and lower into the pycnometer. Fill the pycnometer in the usual manner, as given in 10.2. Remove the syringe and needle and place the pycnometer in the bath for temperature equilibration. Remove excess sample with a thin strip of filter paper or heated draw-off needle, taking care not to remove sample below the calibration mark.
11.5 Close the pycnometer with the glass stopper and immerse it to a point above the calibration mark in the constant-temperature bath, adjusted to the desired temperature within +/-0.01°C. Periodically, or before the liquid expands into the overflow chamber, remove the stopper, raise the pycnometer sufficiently to expose the calibration mark to view, and readjust the liquid level to the mark by withdrawing liquid with thin strips of filter paper. Continue in this manner until expansion has stopped, indicating that the liquid has reached the temperature of the bath. To minimize errors caused by faulty drainage, do not allow the liquid to expand more than 10 mm above the calibration mark at any time. Allow the contents to equilibrate an additional 10 min and draw the level down exactly to the top of the calibration line, avoiding parallax and using a magnifier, if necessary, to obtain good visibility. Remove any liquid adhering to the walls above the calibration mark with filter paper or a pipe cleaner, barely moistened with a suitable solvent if necessary.
11.6 Replace the glass stopper, and proceed as directed in 10.5.
12. Calculation
12.1 Calculate the density of the sample, corrected to vacuum, by the following equation:
Density in vacuum (dt), g/mL = (Ft)(Wt) + C
where:
Ft = calibration factor of the pycnometer at t°C,
Wt = weight of sample, g, in pycnometer at t°C, and
C = vacuum correction, obtained from Table 1.
12.2 Calculate the relative density (specific gravity) of the sample by dividing the density, as obtained in 12.1, by the density of water at the reference temperature obtained from Table 2.
