ASTM D4953 Vapor Pressure of Gasoline and Gasoline-Oxygenate Blends
ASTM D4953 Standard Test Method for Vapor Pressure of Gasoline and Gasoline-Oxygenate Blends (Dry Method)
7. Preparation of Apparatus
7.1 This section applies to both Procedure A and Procedure B.
7.2 Verification of Sample Container Filling - With the sample at a temperature of 0 to 1°C, take the container from the cooling bath or refrigerator and wipe dry with absorbent material. If the container is not transparent, unseal it, and using a suitable gage, confirm that the sample volume equals 70 to 80 % of the container capacity (see Note 4). If the sample is contained in a transparent glass container, verify that the container is 70 to 80 % full by suitable means (see Note 4).
NOTE 4 - For non-transparent containers, one way to confirm that the sample volume equals 70 to 80 % of the container capacity is to use a dipstick that has been pre-marked to indicate the 70 and 80 % container capacities. The dipstick should be of such material that it shows wetting after being immersed and withdrawn from the sample. To confirm the sample volume, insert the dipstick into the sample container so that it touches the bottom of the container at a perpendicular angle, before removing the dipstick. For transparent containers, using a marked ruler or by comparing the sample container to a like container which has the 70 and 80 % levels clearly marked, has been found suitable.
7.2.1 Discard the sample if its volume is less than 70 % of the container capacity.
7.2.2 If the container is more than 80 % full, pour out enough sample to bring the container contents within 70 to 80 % range. Under no circumstance return any of the poured out sample to the container.
7.2.3 Reseal the container, if necessary, and return the sample container to the cooling bath.
7.3 Air Saturation of the Sample in Sample Container:
7.3.1 Transparent Containers Only - Since 7.2 does not require that the sample be opened to verify the sample capacity, it is necessary to unseal the cap momentarily before resealing it, so that the samples in transparent containers are treated the same as samples in non-transparent containers.
7.3.2 With the sample again at a temperature of 0 to 1°C, take the container from the cooling bath or refrigerator, wipe it dry with an absorbent material, remove the cap momentarily, taking care that no water enters, reseal, and shake vigorously. Return it to the cooling bath or refrigerator for a minimum of 2 min.
7.3.3 Repeat 7.3.2 twice more. Return the sample to the cooling bath until the beginning of the procedure.
7.4 Preparation of Liquid Chamber:
7.4.1 Place the stoppered or closed liquid chamber and the sample transfer tube in a refrigerator or cooling bath for sufficient time to allow the chamber and the transfer tube to reach a temperature of 0 to 1°C (32 to 34°F). Keep the liquid chamber upright and not immersed over the top of the coupling threads.
NOTE 5 - Caution: The transfer connection must be kept completely dry during cooling. This can be accomplished by placing the transfer connection in a water tight plastic bag.
7.5 Preparation of the Vapor Chamber
7.5.1 Connect the gage or pressure transducer to the vapor chamber and make a water tight closure of the lower opening of the chamber where the liquid chamber attaches. Make sure that the vent hole in the vapor chamber connection is also securely closed.
NOTE 6 - For some Test Method D 323 apparatus, a Number 6.5 rubber stopper has been found satisfactory. For the horizontal or Herzog apparatus, a Number 3 rubber stopper and a Number 000 cork in the vent hole is satisfactory. Another procedure is to attach a spare liquid chamber to the vapor chamber during the conditioning period. A third alternative is to utilize a cap threaded to match the threads of the vapor chamber. Several apparatus manufacturers have indicated the intention to supply such caps for equipment. In any procedure used, the interior surfaces of the vapor pressure apparatus and the sample must be kept completely free of water.
NOTE 7 - Caution: Making a water tight closure of both the liquid and vapor chambers is extremely important. For some samples containing oxygenated compounds, contact with water can cause phase separation and invalidate results.
7.5.2 Immerse the vapor chamber in a water bath maintained at 37.8 +/- 0.1°C (100 +/- 0.2°F) for not less than 20 min. The top of the vapor chamber must be at least 25 mm (1 in.) below the surface of the water (Procedure A). (In Procedure B the vapor chamber lies horizontally, completely immersed in the water bath.) Do not remove the vapor chamber from the water bath until the liquid chamber has been filled with sample as described in 8.1.
