ASTM D5771 Standard Test Method for Cloud Point of Petroleum Products and Liquid Fuels (Optical Detection Stepped Cooling Method)
11. Procedure
11.1 Set the temperature unit on the apparatus to 1 °C or to 0.1 °C.
NOTE 4 - The temperature unit, in common laboratory practice, is 1 °C. If a higher resolution is desired, 0.1 °C can be selected.
11.2 Using a water bath or oven, bring the sample to be tested to a temperature at least 14 °C above the expected cloud point. When moisture is present in the sample, remove the moisture present by a method, such as filtration through dry lint-free filter paper, until the sample is perfectly clear, but make such filtration at a temperature ofat least 14 °C above the approximate cloud point but otherwise not in excess of 70 °C.
11.3 Pour the clear sample into the test jar to the level mark.
11.4 Place a cork disk at the bottom of the jacket in the appropriate cell and fit a cork ring around the test jar. Use the cork placement guide, if necessary, for the final adjustment. The cork ring must be 25 mm +/- 3.0 mm above the bottom of the test jar.
NOTE 5 - A cork placement guide may be obtained from the apparatus supplier which can assist in proper placement of the cork ring.
11.5 Place the test jar in the appropriate test cell. Attach the detector head according to the manufacturer's instructions.
11.6 Start the test according to the manufacturer's instructions. The instrument shall then automatically adjust the jacket temperature in accordance with Table 1 and begin to optically monitor the specimen for the cloud point. The instrument shall monitor and display the jacket temperature and the specimen temperature during the test procedure.
11.7 The instrument shall continue to monitor and adjust the jacket temperature according to Table 1. The time to move from one jacket temperature level to the next jacket temperature level shall not exceed 200 s, for jacket temperatures down to –52 °C.
NOTE 6 - For lower jacket temperatures, the time to move from one jacket temperature level to the next jacket temperature should not exceed 300 s. Maintain cooling system temperatures as low as possible to attain these jacket temperatures in the shortest time period possible and utilize cooling system with cooling capacity capable of achieving the lowest temperature required.
11.8 The instrument shall detect the cloud point at the bottom of the test jar and record and display the temperature as selected in 11.1. The instrument shall have an audible alarm, such that when a cloud point is detected, it immediately notifies the operator. This function allows the operator to remove the specimen from the instrument and visually inspect the cloud formation and verify the result, if desired.
11.9 After the determination, the instrument shall adjust the jacket temperature to 23 °C +/- 2 °C.
