ASTM D246 Method for Distillation of Creosote and Creosote-Coal Tar Solutions
9. Procedure
9.1 Weigh the flask to the nearest 0.05 g and then weigh 100.0 more or less 0.1 g of the sample into it. Assemble the apparatus as described in Section 8.
9.2 Apply heat to the flask so that, 45 s after the first drop of distillate falls from the end of the condenser, the distillation rate is 80 to 100 drops per minute (Note 1). Maintain this rate throughout the distillation. If the sample contains over 1 % water, heat the flask and contents carefully until the vapor temperature reaches 170°C to distill off the water before continuing the distillation as previously described. Warm the condenser tube whenever necessary to prevent accumulation of solid distillates in the tube.
NOTE 1 - If an electric metronome is not available to measure the distillation rate, not less than 20 drops nor more than 25 drops of distillate shall fall from the end of the condenser in the time interval 45 to 60 s after the first drop or in any given 15-s time interval thereafter.
9.3 Collect the distillate fractions in tared receivers, changing receivers as the thermometer indicates the maximum temperature, corrected as described in 9.4, for each specified fraction. The following fractions are specified:
Up to 210°C
210 to 235°C
235 to 270°C
270 to 315°C
315 to 355°C
9.4 Do not change the position of the thermometer during the distillation. Make no correction for emergent stem of the thermometer, but if the barometric pressure is outside the range from 756 to 765 mm, adjust (but do not report) the temperature in accordance with Table 1.
9.5 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 drop the electric heater a distance of at least 6 in. 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.
9.6 Weigh the receivers containing the distillate fractions to the nearest 0.05 g. Remove the cork and thermometer and weigh the flask and residue to the nearest 0.05 g.
9.7 Should the fraction of 210°C contain water, determine the water volume and calculate the net weight 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:
9.7.1 Transfer the fraction, after weighing, to a tube or cylinder graduated in 0.1 mL. Rinse the receiver several times with benzene, adding the rinsings to the tube or cylinder containing the fraction or,
9.7.2 The fraction to 210°C may be collected in a tared 5-mL graduated cylinder having a flared top. After weighing, add benzene; this will result in a clear separation of the water and oil distillate.
9.8 If tests of the residue are required, replace the cork and thermometer in the flask and 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 the temperature of which does not exceed 150°C. Incline the flask and rotate it so that the fluid residue will flow around the side, 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.
10. Calculation
10.1 Convert the distillation results to the water-free basis by means of the following equations:
Fraction to 210°C:
Percentage (water-free basis) = (F - W) x 100/(100 - W)
Second and Subsequent Fractions Including Residue:
Percentage (water-free basis) = F x 100/(100 - W)
where:
F = fraction or residue, g, and
W = millilitres of water, g, in fraction distilling to 210°C.
10.2 Add the percentages (water-free basis) of the fractions to obtain cumulative percentages to the specified temperatures.
