Antifreeze

antifreeze, substance added to a solvent to lower its freezing point. The solution formed is called an antifreeze mixture. Antifreeze is typically added to water in the cooling system of an internal-combustion engine so that it may be cooled below the freezing point of pure water (32°F; or 0°C;) without freezing. Any substance that dissolves will cause freezing-point depression (see colligative properties); a desirable antifreeze also should not corrode metal parts, attack rubber, become viscous at low temperatures, or evaporate readily at the ordinary engine operating temperature. It should be chemically stable, a good conductor of heat, and a poor conductor of electricity. Ethylene glycol is the most widely used automotive cooling-system antifreeze, although methanol, ethanol, isopropyl alcohol, and propylene glycol are also used. Substances that inhibit corrosion are usually added; antifoaming agents are sometimes added as well. In automotive windshield-washer fluids, an alcohol (e.g., methanol) is usually added to keep the mixture from freezing; it also acts as a solvent to help clean the glass. The brine used in some commercial refrigeration systems is an antifreeze mixture; it is typically a water solution of calcium chloride or propylene glycol.

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antifreeze

Any substance that lowers the freezing point of water, protecting a system from the ill effects of ice formation. Antifreezes such as ethylene glycol or propylene glycol commonly added to water in automobile cooling systems prevent damage to radiators. Additives to prevent freezing of water in gasoline (e.g., Drygas) usually contain methanol or isopropanol. Organisms that must survive freezing temperatures use various chemicals to inhibit ice crystal formation in their cells and tissues: glycerol or dimethyl sulfoxide in insects, glycerol or trehalose in other invertebrates (nematodes, rotifers), and proteins in Antarctic fishes.

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antifreeze

a liquid, usually ethylene glycol (ethanediol), added to cooling water to lower its freezing point, esp for use in an internal-combustion engine

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antifreeze [′an·tē‚frēz]

(chemistry)

A substance added to a liquid to lower its freezing point; the principal automotive antifreeze component is ethylene glycol.

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Antifreeze 

a liquid with a low freezing point, used for cooling internal combustion engines and other equipment operating at temperatures below 0°C. The primary requirements for antifreeze are high heat capacity, thermal conductivity, boiling point, and flash point; low viscosity at low temperatures, small vapor pressure, and as little foaming as possible. In addition, antifreeze must not be very corrosive to the metals from which the cooling system parts are made and must not eat away hose and gasket materials. These requirements are met to a greater or lesser degree by aqueous solutions of ethylene glycol, glycerine, certain alcohols, and other organic compounds as well as by aqueous salt solutions (for instance, calcium chloride).

The best antifreeze materials are aqueous solutions of ethylene glycol with anticorrosion additives to prevent corrosion (such as sodium phosphate). It is possible to obtain mixtures with a freezing point as low as -75°C (66.7 percent ethylene glycol and 33.3 percent water). Upon freezing, such solutions increase in volume insignificantly (0.3 percent with a 55 to 65 percent water content) and when cooled below freezing do not rupture pipes and radiators of the cooling system.

Domestic industry manufactures brands 40 and 65 ethylene glycol antifreeze (freezing points of -40°C and -65°C, respectively) with sodium phosphate and brand 40 M with sodium molybdate.

REFERENCES

Motornye i reaktivnye masía i zhidkosti. Edited by K. K. Papok and E. G. Semenido, 4th ed. Moscow, [1964].
Bobrov, N. N., and P. I. Voropai. Primenenie topliv i smazochnykh materialov, 2nd ed. Moscow, 1968.

V. V. PANOV