ASTM D5188 Standard Test Method for Vapor-Liquid Ratio Temperature Determination of Fuels (Evacuated Chamber and Piston Based Method)
12. Procedure
12.1 When a vacuum pump is used for evacuation, calculate the volume of sample required to give the desired vapor-liquid ratio using Eq 1 (13.1).
12.2 Remove the sample from the cooling bath or refrigerator, dry the exterior of the container with absorbent material, unseal and insert a chilled transfer tube or gas-tight syringe (9.4). Draw a bubble-free aliquot of sample into the syringe or transfer tube and deliver this sample to the test chamber as rapidly as possible. The total time between opening the chilled sample container and inserting/securing the syringe into the sealed test chamber shall not exceed 1 minute.
12.3 Perform the analysis in accordance with the manufacturer's instructions for operation of the instrument.
12.4 Record the temperature reading from the instrument to the nearest 0.1 °C (0.2 °F) after the pressure indicator has remained stable at 101.3 kPa (14.69 psia) for 1 minute.
NOTE 11 - If the measurement is made at a pressure other than 101.3 kPa (14.69 psia) the pressure must be noted.
12.5 Verification of Single Phase Sample - Check the remaining sample from 8.3 for phase separation. If the sample is contained in a transparent container, this observation can be made prior to sample transfer (12.2). If the sample is contained in a non-transparent container, mix the sample thoroughly and immediately pour a portion of the remaining sample into a clear glass container and observe for evidence of phase separation. A hazy appearance is to be carefully distinguished from separation into two distinct phases. The hazy appearance shall not be considered grounds for rejection of the fuel. If a second phase is observed, discard the test and the sample. Hazy samples may be analyzed (see Report section).
13. Calculations
13.1 Use the following equation to calculate vapor-liquid ratio:
V/L = (V - v)/v
where:
V/L = vapor-liquid ratio
V = volume of test chamber, mL, and
v = volume of sample at 0 °C (32 °F), mL.
