ASTM D3142 for Specific Gravity, API Gravity, or Density of Cutback Asphalts
ASTM D3142 Standard Test Method for Specific Gravity, API Gravity, or Density of Cutback Asphalts by Hydrometer Method
10. Procedure
10.1 Select the test temperature in accordance with the indications given in Section 9. Heat the sample in an oven to within 3°C [5°F] of the test temperature but without exceeding it. Cover the container with a loose-fitting cover to prevent solvent evaporation. Bring the hydrometer cylinder and thermometer to approximately the same temperature as the sample to be tested.
10.2 Transfer the sample to a clean hydrometer cylinder (Note 4) without splashing, to avoid the formation of air bubbles, and to reduce to a minimum the evaporation of the lower boiling constituents of the more volatile samples. Remove any air bubbles formed, after they have collected on the surface of the sample, by touching them with a piece of clean filter paper before inserting the hydrometer.
NOTE 4 - Volume and density correction tables are based on an average coefficient of expansion for a number of typical materials. Since the same coefficients were used in computing both sets of tables, corrections made over the same temperature interval minimize errors arising from possible differences between the coefficients of the material under test and the standard coefficients. This effect becomes more important as temperatures diverge significantly from the standard table temperatures of 15°C or 60°F.
10.3 Place the cylinder containing the sample in the constant-temperature bath previously brought up to the test temperature ±0.5°C [1.0°F]. Allow sufficient time for the sample to reach the bath temperature ±0.5°C [1.0°F] and verify its temperature with the thermometric device. If a thermohydrometer is used, it may be lowered into the sample at this point instead of the thermometric device. As soon as a steady thermometer reading is obtained, record the temperature of the sample to the nearest 0.2°C [0.5°F].
10.4 Lower the hydrometer gently into the sample. Take care to avoid wetting the stem above the level to which it will be immersed in the liquid. Allow sufficient time for the hydrometer to become completely stationary and for all air bubbles to come to the surface. This is particularly necessary in the case of the more viscous samples.
10.5 When the hydrometer has come to rest, floating freely away from the walls of the cylinder, read the hydrometer to the nearest scale division. Take the reading by observing with the eye slightly above the plane of the surface of the liquid, the point on the hydrometer scale to which the sample rises. This reading, at the top of the meniscus, requires correction since hydrometers are calibrated to be read at the principal surface of the liquid. The corrections for the particular hydrometer in use may be determined by observing the maximum height above the principal surface of the liquid to which oil rises on the hydrometer scale when the hydrometer in question is immersed in a transparent oil having a surface tension similar to that of the sample under test. For routine work, determine the height of the meniscus by sighting across the principal surface of the liquid and estimating the rise of the meniscus on the hydrometer scale.
10.6 Immediately after observing the hydrometer scale value, cautiously stir the sample with the thermometric device. Record the temperature of the sample to the nearest 0.2°C [0.5°F] (Note 5). Should this temperature differ from the previous reading by more than 0.5°C [1.0°F], repeat the hydrometer and the temperature observations until the temperature becomes stable within 0.5°C [1.0°F].
NOTE 5 - After use at a temperature higher than 40°C [100°F], allow all hydrometers of the lead shot in wax type to drain and cool in a vertical position.
11. Calculation
11.1 Apply any relevant corrections to the observed thermometer reading (for scale and bulb) and to the hydrometer reading (scale). Make the appropriate correction to the observed hydrometer reading. Record the specific gravity to the nearest 0.001, the API gravity to the nearest 0.1°, or the density to the nearest 1 kg/m3. After application of any relevant corrections, record to the nearest 0.5°C [1.0°F] the mean of the temperature values observed immediately before and after the final hydrometer reading.
11.2 To convert the observed hydrometer reading to density to standard temperature, use the following guidance to select the correct table from Guide D1250 and ASTM D1250 Petroleum Measurement Tables:
11.2.1 When an API gravity hydrometer has been used, use Table 5A to convert the hydrometer reading to the API gravity. Then, if desired, use Table 3 to obtain the specific gravity 60/60°F or the density at 15°C.
11.2.2 When a specific gravity hydrometer has been used, use Table 23A to convert the hydrometer reading to the specific gravity 60/60°F. Then, if desired, use Table 21 to obtain the API gravity at 60°F or the density at 15°C.
11.2.3 When a density scaled hydrometer has been used, use Table 53A to obtain the density at 15°C. Then, if desired, use Table 51 to obtain specific gravity 60/60°F or API gravity at 60°F.
