ASTM D20 Standard Test Method for Distillation of Road Tars
8. Procedure
8.1 Weigh the flask (along with the thermometer and cork) to the nearest 0.1 g and then weigh 100.0 ± 0.1 g of the sample into the flask.
8.2 Apply heat to the flask so that the first drop of distillate (oil or water) falls from the end of the condenser tube in 5 to 15 min. Within 2 min after the first drop, adjust the rate of distillation, and subsequently maintain the rate, so that from 50 to 70 drops per min fall from the end of the condenser. Warm the condenser tube whenever necessary to prevent accumulation of solid distillates in the tube.
8.3 Collect the distillate fractions in tared receivers, changing receivers as the thermometer indicates the maximum temperature, corrected as described in 8.4, for each specified fraction. The following fractions are usually specified.
Up to 170°C
170 to 235°C
235 to 270°C
270 to 300°C
Residue at 300°C
Fractions at other temperatures, such as 170 to 200°C and 200 to 235°C, or 300 to 355°C and residue at 355°C, are sometimes required.
8.4 Do not change the position of the thermometer during the distillation. Make no correction for the emergent stem of the thermometer, but if the barometric pressure is outside the range of 756 to 765, adjust (but do not report) the temperature in accordance with Table 1.
8.5 When the maximum temperature specified for the test is indicated by the thermometer, immediately remove the flame and the flask-shield cover; or when the electric heater is used as a source of heat, immediately remove the flask shield cover and lower the heater at least 150 mm. Allow the apparatus to cool, for at least 5 min, or until no vapors are visible. Drain any oil remaining in the condenser tube into the receiver containing the last fraction.
8.6 Weigh the receivers containing the distillate fractions to the nearest 0.1 g. Weigh the flask (with the thermometer in place) and residue to the nearest 0.1 g.
8.7 Should the fraction to 170°C contain water, determine the water volume and calculate the new mass of oil distillate, assuming that 1 mL of water weighs 1 g. The amount of water contained in this fraction may be determined by either of the following methods.
8.7.1 Transfer the fraction after weighing, to a tube or cylinder graduated in 0.1 mL. Rinse the receiver several times with toluene, adding the rinsings to the tube or cylinder containing the fraction or,
8.7.2 The fraction of 170°C may be collected in a tared graduated cylinder having a flared top. After weighing, add toluene which will result in a clear separation of the water and oil distillate.
8.8 If the residue from distillation is required for further testing, lower the thermometer until its bulb is in the liquid residue. If the residue is not completely fluid, heat it carefully to a temperature not exceeding 150°C by holding the bulb of the flask over a wire gauze heated by a gas burner or by immersion in a suitable bath whose temperature does not exceed 150°C. Incline the flask and rotate it so that the fluid residue will flow around the sides, and collect any oils that have condensed on the upper surfaces of the flask. Mix the contents of the flask until they are homogeneous. Allow the residue to cool to a temperature at which it can be readily poured from the flask without loss of volatile material and then pour it into the desired testing equipment or into a suitable receptacle. Cover the receptacle.
9. Calculation
9.1 Convert the distillation results to a water-free basis, D, in %, as follows:
D = (F - W) x [100/(100 - W)]
Second and Subsequent Fractions Including Residue:
D = F x [100/(100 - W)]
where:
F = mass of the fraction or residue, g and
W = millilitres of water, expressed as grams, in the fraction distilling to 170°C.
