ASTM D611 standard test methods for aniline point and mixed aniline point of petroleum products and hydrocarbon solvents
6. Apparatus
6.1 For details of the aniline point apparatus required for each method see:
Annex A1 for Test Method A
Annex A2 for Test Method B
Annex A3 for Test Method C
Annex A4 for Test Method D
Annex A5 for Test Method E
NOTE 1 - Alternative apparatus may be used, such as the U-tube method for dark oils, provided it has been shown to give results of the same precision and accuracy as those described in the annexes.
6.2 Heating and Cooling Bath - A suitable air bath, a nonvolatile, transparent liquid bath, or an infrared lamp (250 to 375 W), provided with means for controlling the rate of heating.
NOTE 2 - Water should not be used as either a heating or cooling medium since aniline is hygroscopic and moist aniline will give erroneous test results. For example, the aniline point of the n-heptane reagent as measured with aniline containing 0.1 volume % water is approximately 0.5°C (0.9°F) higher than that measured with dry aniline. If the aniline point is below the dew point of the atmosphere, pass a slow stream of dry inert gas into the aniline point tube to blanket the aniline-sample mixture.
6.3 Thermometers, or other temperature sensing devices, such as thermocouples or platinum resistance thermometers that cover the temperamental range of interest and can provide equivalent or better accuracy and precision, may be used in place of the thermometers having the following ranges and conforming to the requirements of the designated ASTM or IP specification:
6.4 Pipets, or equivalent volume dispensing devices, capable of delivering volumes with capacities of 10 more or less 0.04 mL and 5 more or less 0.02 mL, for use in the test.
6.5 Balance - A laboratory balance sensitive to 0.01 g, suitable for weighing the tube and sample when the sample cannot be pipetted conveniently.
6.6 Safety Goggles.
6.7 Plastic Gloves, impervious to aniline.
7. Reagents
7.1 Aniline (Warning - Aniline should not be pipetted directly by mouth because of its extreme toxicity. Aniline is also toxic by absorption through the skin even in very small quantities, and should be handled with great caution.) Distill chemically pure aniline and dry as needed to meet purity requirements for use, discarding the first and last 10 %. Aniline thus prepared when tested with n-heptane according to Section 9 shall give an aniline point of 69.3 more or less 0.2°C (156.7 more or less 0.4°F) as determined from the average of two independent tests having a difference of not more than 0.1°C (0.2°F).
NOTE 3 - For routine purposes the distillation process is not mandatory provided the aniline meets the requirements of the test with n-heptane.
NOTE 4 - As an alternative to distilling the aniline on the day of use, the aniline may be distilled as described in 7.1, collecting the distillate in ampoules, sealing the ampoules under vacuum or dry nitrogen, and storing in a cool dark place for future use. Alternatively, distillate may be stored under dry nitrogen in a glass bottle or in single use ampules kept in a cool, dark place. In either case, rigid precaution must be taken to avoid contamination from atmospheric moisture (Note 2). It is believed that under these conditions the aniline will remain unchanged for a period exceeding 6 months.
7.2 Calcium Sulfate, anhydrous.
7.3 n-Heptane, spectroscopic or HPLC grade. (Warning - Flammable. Harmful if inhaled. Keep away from heat, sparks, and open flame. Keep container closed. Use with adequate ventilation. Avoid prolonged breathing of vapor or spray mist. Avoid prolonged or repeated skin contact.)
8. Sample
8.1 Dry the sample by shaking vigorously for 3 to 5 min with about 10 volume % of a suitable drying agent such as anhydrous calcium sulfate or anhydrous sodium sulfate. Reduce the viscosity of viscous samples by warming to a temperature below that which would cause the loss of light ends or the dehydration of the drying agent. Remove any suspended drying agent by use of a centrifuge or by filtration. Heat samples containing separated wax until they are homogeneous and keep heated during filtration or centrifugation to ensure against separation of wax. When suspended water is visibly present and the sample material is known to dissolve less than 0.03 mass % of water, the use of a centrifuge for the removal of suspended water is an acceptable procedure.