12. Procedure
12.1 Weigh the recommended amount of sample (usually 2.5 g) into a 50-mL beaker and record weight (W1).
12.2 Add 2.0 mL of refined quinoline per gram of sample to beaker.
12.3 Place thermometer 0 to 300°F (150°C) (6 in. length) into solution and heat on steam bath to 167 ± 10°F (75 ± 5°C) for not less than 15 nor more than 20 min. Closely inspect the thermometer and bottom of the beaker for undissolved pitch and stir so that all of the pitch is brought into solution.
12.4 Place gaskets into the pressure vessel.
12.5 Start to heat block with steam (see 5.1 and Fig. 2).
12.6 Weigh a 3A2 Berlin crucible and record mass (W2).
12.7 Place the preweighed crucible in the pressure vessel and then put crucible collar on (see 5.1 and Fig. 3).
12.8 When the quinoline-pitch solution has completed the heating cycle (see 12.3), pour the solution into the crucible, decanting it alongside the thermometer. Wash down the thermometer and beaker with 5 to 10 mL of quinoline and place on the steam bath.
12.9 Place the lid of the pressure filter with the adjustable plunger on the pressure vessel. The plunger shall be adjusted so that there is about 1/8- to 1/4-in. gap between the lid and the flat gasket (see Fig. 1) of block. To close, force down by hand and attach clamp.
NOTE 1 - Sealing of the crucible is a trial-and-error process. Excessive pressure could cause the crucible to be pushed past the O-rings during filtration or not allow complete sealing of the lid. Insufficient pressure of the plunger could cause leaks around the O-rings.
12.10 Add 10 psig of nitrogen using the pressure controller to pressurize the vessel to 10 psig with nitrogen. One may see slight bubbling from the indicator before the filtrate can be seen coming from the drain. Once the filtrate is flowing, pressure can be increased to 30 psig gradually. Nitrogen may bubble slowly (caused by volume displacement in the collecting flask) through the water seal and may bubble fast when filtration is completed. When filtrate stops coming out of bottom, shut off nitrogen and remove lid.
NOTE 2 - In some cases, nitrogen stops bubbling although there is no draining of the filtrate. The filtration is actually completed, the quinoline insolubles have compacted on the bottom (filter cake) of the crucible and do not let nitrogen pass through. By increasing the pressure, nitrogen will eventually break through the filter cake.
12.11 Continue filtering the sample as described in 12.8 to 12.10 until the filtrate is clear. This usually will take about three washings of the beaker. When the third or last washing is poured into the crucible, rinse the beaker with the wash bottle, allowing the solution to run into the crucible to remove any carbon deposits. Filter the rinses.
12.12 When the last filtration is complete, shut the steam and nitrogen off. Remove the lid and start cooling the block with water (it takes approximately 5 min to cool the block and crucible).
12.13 Once cool, fill the crucible to about three quarters of its volume with acetone. Place lid on and follow 12.10 to filter. Perform this step three times.
12.14 When acetone rinses are complete, shut off the nitrogen, remove the lid, remove the crucible, and wipe sides with a paper towel containing acetone to remove any traces of quinoline. Place crucible in an oven at 221°F (105°C) for a minimum of 30 min, preferably 1 h. Remove, place in a desiccator, and allow to cool for 30 min.
12.15 Weigh the crucible containing quinoline insolubles and record the mass (W3).
NOTE 3 - For pitches yielding slow-filtering quinoline insolubles, a higher pressure may be used of up to 50 but not to exceed 75 psig. Under these conditions, a stainless steel disk with a 1/8-in. hole is added to the bottom of the block. Under high pressure, the crucible can be forced through O-rings. The stainless steel plate reduces the distance the crucible will travel to a minimum and thus avoids breakage and sample loss.
13. Calculation
13.1 Calculate the quinoline-insoluble (QI) content as follows:
QI, % = [(W3 - W2)/W1] x 100
where:
W3 = mass of crucible with QI, g;
W2 = mass of the crucible, g; and
W1 = mass of the sample, g.
13.2 If the QI was determined on a wet tar sample (see 9.3.2), correct the QI value determined in 13.1 to a dry-tar basis as follows:
