ASTM D2533 Test Method for Vapor-Liquid Ratio of Spark-Ignition Engine Fuels
8. Handling of Samples
8.1 General:
8.1.1 Conduct bulk sampling to obtain the laboratory samples in accordance with Practice D4057 except for gasoline-oxygenate blends where water displacement is not used. The extreme sensitivity of T (V/L) measurements to losses through evaporation and resulting changes in composition is such as to require utmost precaution and the most meticulous care in handling the samples.

NOTE 7 - Warning: Extremely flammable, harmful in inhaled or ingested. Skin irritant on repeated contact. Aspiration hazard.

8.1.2 The size of the sample container from which the sample is taken shall be 1 L (1 qt). It shall be 70 % to 80 % filled with sample.

8.1.3 The precision statement was derived using samples in 1 L (1 qt) containers. However, samples taken in containers of other sizes prescribed in Practice D4057 can be used if it is recognized that the precision could be affected. In the case of referee testing, the 1 L (1 qt) sample size is mandatory.

8.1.4 Perform the T (V/L) determination on the first test specimen withdrawn from the sample container. Do not use the remaining sample in the container for a second T (V/L) determination. If a second determination is necessary, obtain a new sample.

8.1.5 Protect samples from excessive temperature prior to testing. This can be accomplished by storage in an appropriate ice bath or refrigerator.

8.1.6 Do not test samples in leaky containers. Discard and obtain a new sample if leaks are detected.

8.2 Sampling Temperature - Cool the sample container and contents in an ice bath or refrigerator 0 to 1°C (32 to 34°F) prior to opening the sample container. Ensure sufficient time to reach this temperature by direct measurement of a similar liquid in a like container placed in the cooling bath at the same time as the sample.

8.3 Verification of Sample Container Filling:
8.3.1 After the sample reaches thermal equilibrium at 0 to 1°C, take the container from the cooling bath or refrigerator and wipe dry with an 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 8). If the sample is contained in a transparent glass container, verify that the container is 70 to 80 % full by suitable means (see Note 8).

NOTE 8 - 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.

8.3.2 Discard the sample if the container is filled to less than 70 %, by volume, of the container capacity.

8.3.3 If the container is filled to more than 80 %, by volume, of the container capacity, pour out enough sample to bring the container contents to within the 70 to 80 % volume range. Do not return any sample to the container once it has been withdrawn.

8.3.4 Reseal the container, if necessary, and return it to the cooling bath or refrigerator.

8.4 Air Saturation of the Sample in the Sample Container:
8.4.1 Non-Transparent Containers - With the sample again at a temperature of 0 to 1°C, take the container from the cooling bath, 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.

8.4.2 Transparent Containers Only - Since 8.3.1 does not require that the sample container be opened to verify the sample capacity, it is necessary to unseal the cap momentarily before resealing it, so that samples in transparent containers are treated the same as samples in non-transparent containers. After performing this task, proceed with 8.4.1.

9. Calibration
9.1 Calibrate the V/L buret and the hypodermic syringe and correct the subsequent experimental readings from the calibration curves obtained.

9.2 Fill the hypodermic syringe with air-free distilled water at 77°F (25°C), expel any air bubbles, and depress the plunger exactly to a calibration mark. Discharge the contents, to the bottom of plunger travel, into a weighing vial and weigh. Repeat at 0.2-mL intervals from 0.2 to 1.0 mL and average the results from two or more determinations. Calculate the volumes at 32°F (0°C) from the weights of water (Note 7) and prepare a calibration curve.

NOTE 9 - One gram of water at 77°F (25°C) = 1.0036 mL volume at 32°F (0°C) in resistance glass or 1.0038 mL volume at 32°F (0°C) in borosilicate glass.

9.3 Clean the V/L buret thoroughly, rinse with distilled water, attach a capillary stopcock with rubber tubing snug to the side arm, and fill the system completely with air-free distilled water at 77°F (25°C). Calibrate at 5-mL intervals starting from the bottom of the buret stopcock (Note 9), by weighing water drained through the capillary stopcock into weighing vials. Repeat and average for two or more determinations. Calculate the volumes at 122°F (50°C) from the weights of water (Note 10) and prepare a calibration curve.

NOTE 10 - Use of the calibration stopper described in 6.1 facilitates setting the water level at the bottom of the stopcock.

NOTE 11 - One gram of water at 77°F (25°C) = 1.0042 mL volume at 122°F (50°C) in borosilicate glass.

10. Preparation for Test
10.1 Cleaning Equipment - Before assembly, thoroughly clean and dry all the equipment, including burets, hypodermic syringes, leveling bulbs, and connecting tubing. Lubricate the buret stopcock with high-vacuum silicone stopcock grease and attach a spring or rubber band to hold securely in place. Thereafter, to clean the buret between tests, rinse thoroughly by flushing with water (Note 11), then with acetone, and dry with air. Clean the hypodermic syringe and needle with acetone and dry in an air stream.

NOTE 12 - If a film is noted in the buret, clean it further with sodium dichromate-sulfuric acid solution. Warning - Causes severe burns. A recognized carcinogen. A strong oxidizer. Contact with organic material may cause fire.

10.2 Filling System With Glycerol (Mercury) - Connect the leveling bulb to the buret with rubber tubing, fill the bulb with clean, dry glycerol (mercury) at room temperature and attach the air-drying device. If mercury is used, be certain that the drying tube contains mercury vapor absorbent (see 6.2.1). Draw glycerol (mercury) into the buret by applying vacuum to the stopcock, and expel all air bubbles from the tubing and rubber septum attachment. It may be necessary to loosen the rubber septum to release air trapped therein.

10.3 Preparation of Apparatus for Subsequent Tests - Due to the partial solubility of certain oxygenates in the glycerol during testing, separate methods are used for subsequent test preparation using glycerol or mercury as the containing fluid.
10.3.1 Glycerol Containing Fluid - The glycerol in the buret is replaced between each test. Following the completion of V/L measurements with a fuel, allow the buret to cool until the vapor has condensed and glycerol has refilled the buret. Clamp the tubing between the leveling bulb and the buret as near the buret as possible. Remove the buret from the tubing, open the stopcock and pour the glycerol out of the buret. Fill a clean buret for the next test as described in 10.2. Add new, dry glycerol to the leveling bulb to replace the displaced used glycerol.

10.3.2 Mercury Containing Fluid - Following the completion of V/L measurements with a fuel, allow the buret to cool until the vapor has condensed and mercury has refilled the buret. While slowly lowering the leveling bulb, slowly open the stopcock and allow all but a few millilitres of mercury to flow back into the leveling bulb. Apply a pinch clamp to the rubber tubing as near the buret as possible and remove the buret. Attach the rubber tubing to a clean buret, and fill the buret as described in 10.2. Add new mercury to the leveling bulb to replace the displaced mercury as needed.

10.4 Preparation of Hypodermic Syringe - Assemble the syringe and needle and insert the needle tip in a small rubber stopper. Cover with drained chipped ice or chill by other means to 32 to 36°F (0 to 2°C).

10.5 Adjustment of Constant-Temperature Bath - Adjust the water bath to the desired test temperature and maintain at that temperature +/-0.2°F (0.1°C).