ASTM D1839 Standard Test Method for Amyl Nitrate in Diesel Fuels
10. Procedure
10.1 Weigh into a separatory funnel a sample of diesel fuel to the nearest 0.1 mg, not exceeding 2 mL (Note 4), and not containing more than 1.0 mg of amyl nitrate. Add 2 mL of the m-xylenol solution and shake thoroughly. Add 50 mL of H2SO4. Shake for 30 min on the automatic shaking machine. Transfer the contents of the separatory funnel to the round-bottom flask and wash the funnel with 100 mL of water, combining this rinse with the solution in the flask.
NOTE 4 - Incomplete reaction will take place if more than 2 mL of sample is used.
10.2 With the apparatus assembled as shown in Fig. 1, distill the sample into a 50-mL volumetric flask containing 5 mL of NaOH solution. Collect 40 mL of distillate. Cool, and dilute to volume with water, allowing any floating diesel fuel to be above the mark.
NOTE 5 - When the solution is not yellow, check the pH. When it is not alkaline, add additional NaOH solution.
10.3 Transfer the solution to a separatory funnel and extract with several portions of ether to remove the diesel fuel that otherwise would cause a turbid water layer.
10.4 Filter the water layer through a coarse-texture paper into an absorption cell and measure its absorbance at 452 nm with respect to water (Note 6). Subtract a blank (Note 7) from the reading and read the milligrams of amyl nitrate from the calibration curve (Section 8).
NOTE 6 - The color developed is stable for several hours. It obeys Beer's law over the range from 0.2 to 2.0 mg of amyl nitrate.
NOTE 7 - Obtain a blank by performing the analysis on the samples of diesel fuel and the reagents without the amyl nitrate present. A blank of 0.019 absorbance can be used since it is the average obtained on a number of representative diesel fuels.
11. Calculation
11.1 Calculate the amyl nitrate present in the sample as follows:
Amyl nitrate, mass % = 100A/1000W = A/10W
Amyl nitrate, vol % = BD/C
where:
A = milligrams of amyl nitrate obtained from the calibration curve,
B = mass percent of amyl nitrate obtained from Eq 1,
C = density of amyl nitrate (0.998 at 20°C),
D = density of diesel fuel sampled at 20°C, and
W = grams of sample used.
