ASTM D1018 standard test method for hydrogen in petroleum fractions
8. Procedure
8.1 Connect the charged absorbers to each other and to the chimney delivery tube as shown in the complete assembly of the apparatus in Fig. 2. Attach the U-tube containing anhydrous calcium sulfate to the exit end of the second absorber to eliminate diffusion of water vapor back into the system. Immerse the lower half of the absorbers into the ice-water bath, connect the air flow system to the chimney, and purge the system with air for 15 min (Warning - see 5.5.) At the end of the purging period, turn off the air flow, close the absorbers, and remove them from the train. Allow the absorbers to reach room temperature, gently wipe each with a lintfree dry cloth, and place them beside the balance case for 30 min or more. Open the absorbers for a moment to equalize the pressure, close, and weigh to the nearest 1 mg.
8.2 While the absorbers are standing, the lamp may be prepared. Thread the burner with the proper number of wick strands (see Note 3) by drawing the strand through the burner tube with a small metal hook. Trim the wick as closely as possible to the top of the burner, and draw the trimmed wick down until it is flush with or slightly below the top of the burner. Pipet approximately 5 mL of test specimen into the burner flask, and insert the prepared burner into the flask. Cap the burner with its glass cap, and close the burner air inlet with a rubber policeman. Allow the sample to rise by capillary action to the top of the wick.
NOTE 3 - The burning characteristics of the flame are dependent upon the flow of air to the burner, the volatility of the test specimen, the tightness of the wick in the burner tube, and the position of the wick relative to the top of the burner. The latter two factors can be established before an actual determination is made so that the flame can be controlled by the rate of air flow. A tightly fitting wick is required for highly volatile samples; also, the wick may have to be drawn down several millimetres below the top of the burner tube. Extremely volatile test specimens (Warning - Extremely flammable.) may require immersion of the burner flask in an ice-water bath during the burning period. A more loosely fitting wick is required for less volatile test specimens, and in some instances the burner flask may require warming to ensure an even flow of test specimen fuel to the burner. In any case, the flame must burn smoothly and symmetrically without jets in the inner cone or smoke on the outer fringes.
8.3 Connect the weighed absorbers to the chimney tube, attach the Drierite tube, and immerse the absorbers in the ice-water bath.
8.4 Weigh the assembled lamp quickly to the nearest 1 mg and bring it immediately to the absorption train. Open the absorbers in the train. Remove the cap and rubber policeman from the lamp, and connect the air flow to the burner. Ignite the lamp with a microburner, and rapidly adjust the air flow until a symmetrical nonsmoking flame is obtained. Immediately insert the lamp in the chimney, using rubber bands or small coil springs to hold the lamp in place. Record to the nearest second the time that elapsed between ignition of the burner and insertion of the lamp in the chimney as lost burning time. The flame may require further minor adjustment in rate of air flow after it has been inserted in the chimney.
8.5 After the desired amount (2 to 3 g) of test specimen has been burned, interrupt the air flow, immediately remove the burner from the chimney, cap it, and replace the rubber policeman. Note and record the time for the complete analysis. As quickly as possible, connect the air line to a clean, thoroughly dry, assembled lamp and insert it in the chimney.
8.6 Weigh the lamp containing the test specimen to the nearest 1 mg.
8.7 Purge the system with purified air for a period of 5 min. If any condensed water is visible in the chimney delivery tube, gently heat the tube with a microburner until all moisture has been vaporized and swept into the absorbers. At the end of the purging period, turn off the air flow, close the absorbers, and remove them from the train. Allow the absorbers to reach room temperature, wipe each with a lint-free dry cloth, equilibrate, and weigh to the nearest 1 mg.
9. Calculation
9.1 Correct the mass of water formed for the lost burning time as follows:
W = w x [t/(t - s)]
where:
W = corrected grams of water collected,
w = grams of water absorbed,
t = time in seconds for complete analysis, and
s = lost burning time in seconds.
9.2 Calculate the hydrogen content of the sample as follows:
Hydrogen, weight % = (W x 11.191)/S
where:
W = corrected grams of water collected, and
S = grams of sample burned.
