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Automatic Freeze Point Determination in Ethylene Glycol Based Engine Coolants

Automatic equipment based on optical detection has been used for petroleum products successfully. Examples include ASTM D5773 Standard Test Method for Cloud Point Determination of Petroleum Products and ASTM D5972 Standard Test Method for the Freezing Point of Aviation Fuels. Recently it has been shown that the technology can be extended to engine coolants1. The determination of freezing point in aqueous ethylene glycol based systems is imperfectly understood and complicated by non-equilibrium solidification. The current ASTM D 1177-94 method includes manual seeding to overcome this but requires a cryogenic bath, time and considerable operator skill. Experimentally determined aqueous ethylene glycol freezing points show good agreement between laboratories only to approximately 60 wt %. In the 58 wt % to 80 wt % region, one, two and even three eutectics have been reported at varying temperatures.