ASTM D2001 Test Method for Depentanization of Gasoline and Naphthas
7. Procedure
7.1 Lubricate the joint at the bottom of the column with a hydrocarbon-insoluble grease, such as silicone, starch-glycerol, or metallic soap. Place the heating mantle around the flask. With a 50-mL graduated cylinder, measure 50 mL of the sample. Determine its temperature, and transfer it to the flask. Connect the flask immediately to the column.
7.2 Connect the mantle, through the variable transformer, to the power supply.
7.3 Apply heat to the contents of the flask at a uniform rate.
NOTE 2 - With the apparatus prepared as described in Section 6, a setting of 30 on the transformer usually provides a satisfactory initial heating rate; voltage is increased as required.
7.4 As soon as drops of liquid reflux form at the column head, adjust the position of the condenser so that one drip-tip feeds to the take-off line, and the other back to the (Warning - Extremely flammable liquid.) column. The reflux condenser remains in this position throughout the distillation to provide about a 1 + 1 reflux ratio.
NOTE 3 - Low-boiling light ends will condense on the light-ends trap and collect in the receiver before drops of liquid reflux form at the column head.
7.5 The distillation rate should not exceed 30 to 40 drops/30 s from each tip of the reflux condenser.
7.6 Continue the distillation until the thermometer indicates a temperature of 49°C (120°F). When this temperature is reached, shut off the heat and drop the lower portion of the heating mantle. Turn the reflux condenser so that drops from both drippers are returned to the column. Direct a stream of air on the top surface of the flask. Perform the above steps in rapid succession.
7.7 Allow the column to drain and the contents of the flask to cool for 30 min.
7.8 Remove the flask from the column, and carefully transfer the contents to the same graduated cylinder which was used to measure the charge. Measure the volume of the bottoms fraction and determine its temperature.
8. Calculation
8.1 If the temperatures of the distillation charge and bottoms differ by more than 11°C (20°F), correct the measured volumes to volumes at 15°C (60°F) by Guide D1250.
8.2 Calculate the volume of bottoms in percent as follows:
Volume of bottoms, percent = (A/B) x 100
where:
A = volume of bottoms, mL and
B = volume of the charge, mL.
