ASTM D5772 Standard Test Method for Cloud Point of Petroleum Products and Liquid Fuels (Linear Cooling Rate Method)
11. Procedure
11.1 Pour at least 20 mL of the sample into the beaker. When necessary, heat the sample in a water bath or oven until it is just sufficiently fluid to pour into the beaker.
11.2 Place the beaker under the entrance of the test cell and start the test in accordance with the manufacturer's instructions.
11.3 When the expected cloud point is known to be above 25 °C, preselect a starting temperature which is at least 14 °C above the expected cloud point. The highest starting temperature that can be programmed is 70 °C.
11.4 When the expected cloud point is known to be at or below 25 °C, the test duration can be shortened by preselecting a starting temperature which is at least 14 °C above the expected cloud point. The lowest starting temperature that can be programmed is 20 °C.
11.5 When the expected cloud point is not known, preselect a starting temperature of 40 °C. The apparatus automatically heats the test specimen to approximately 40 °C when a starting temperature is not selected. When the expected cloud point is not known and the sample needs to be heated before transferring into the test specimen beaker, preselect a starting temperature of 70 °C.
11.6 A portion of the sample is drawn into the test cell. Initially, the specimen is heated to 40 °C or to a starting temperature preselected by the operator between 20 °C and 70 °C. The flow of the cooling fluid from the circulating bath is then regulated to maintain the rate ofcooling ofthe specimen at 1 °C +/- 0.2 °C per min (see Note 2). The specimen is continuously monitored by the optical light barrier and the specimen temperature is continuously displayed. At the detection ofthe automatic cloud point, the temperature the specimen attained, to within 0.1 °C resolution, is held on the digital display until cleared by the operator. The specimen is then heated to 40 °C or to the preselected starting temperature.
NOTE 2 - Although the apparatus is capable of faster cooling rates of 2 °C or 3 °C/min, the interlaboratory program does not address the equivalency and precision of results using these cooling rates.
11.7 Clean the test cell by flushing solvents through the cell and then dry with clean air according to the manufacturer's instructions.
NOTE 3 - Some apparatus is capable of automatic cleaning of the test cell and automatic sample changing.
