ASTM D1177 Test Method for Freezing Point of Aqueous Engine Coolants
6. Apparatus
6.1 Freezing Point Apparatus, shown assembled in Fig. 1, consisting of the following:
6.1.1 Cooling Bath, in which the refrigerant is contained, consisting of a standard 1.9-L (2-qt) Dewar flask. The flask may be silvered or unsilvered, and is supported in a close-fitting container. A pad of glass wool is placed in the bottom of the flask to protect it from damage by tip of freezing tube.
6.1.2 Freezing Tube consisting of a 200-mL (6.8-oz.) unevacuated, unsilvered Dewar flask. The tube is closed by a cork having a central hole for the thermocouple or thermometer, a second hole placed to one side for passage of the stirring rod, and a third hole for introducing wire for seeding at appropriate time.
6.1.3 Stirring Mechanism, consisting of a five-coil stirrer formed of stainless steel wire 1.6 mm (1/16 in.) in diameter. The coils are so spaced that, in the extreme upward position during operation, no coils are exposed above the surface of the sample. The stirrer is agitated by means of an ordinary windshield wiper motor or other motor devices, operating through suitable linkages so as to provide linear motion of the stirrer. The length of the stroke is adjusted so that the coil just clears the bottom of the freezing-point tube at low point of the stroke.
6.1.4 Temperature Measurement - A resistance thermometer or a multi-junction copper-constantan thermocouple may be used with suitable measuring instruments, providing these give an over-all sensitivity of 0.1°C (0.2°F). The instrument shall be calibrated before each series of determinations by using suitable reference standards. Platinum resistance thermometers have been adopted as a standard by the National Institute of Standards and Technology (NIST) and are recommended for this standard.
NOTE 3 - ASTM Coolant Freezing Point Thermometer having a range from -37 to + 2°C (-35 to + 35°F) or -54 to -15°C (-65 to + 5°F) and conforming to the requirements for Thermometers 75C or 76C as prescribed in Specifications E 1, may be used where less accuracy is acceptable provided reference standards are used for calibration purposes.
7. Refrigerant
7.1 The refrigerant shall consist of solid carbon dioxide in alcohol or in other suitable bath liquids.
NOTE 4 - A layer of dry ice, at least 13 mm (1/2 in.) thick, must be maintained in the bottom or on the top of the cooling bath during a determination, depending on the bath liquid used. Adequate precautions should be taken against fire hazards or toxic effects of bath liquids, or both.
7.2 Liquid nitrogen may be used as the refrigerant when the freezing point of the coolant is -46°C (-50°F) or lower.
NOTE 5 - Warning: The liquid nitrogen should be discarded after each day's use to avoid the possibility of explosion due to dissolved oxygen and inadvertent mixing with organic coolant materials.
