Antifreeze

Antifreeze is used in internal combustion engines, and for many other heat transfer applications, such as electronics cooling and chillers for HVAC. boiling point of the coolant, which should then be more properly referred to as "anti-boil", and as anti-freeze decreases and increases both properties, respectively, "colligative agent" more accurately describes the liquid. The term "engine coolant" is widely used in industry.

Agents

Methanol

Until the 1930s, specific heat capacity led to considerably less cooling than water alone. Also, the concentration of methanol would tend to be reduced over time due to its greater tendency to evaporate than the water with which it was mixed.

Ethylene glycol

calcium oxalate crystals in the kidneys and can cause acute renal failure and death. All spills should be cleaned, or else an area in which it may be present should be kept inaccessible.

Should ingestion of antifreeze occur, fomepizole), its popularity for this application is greatly in decline. ^[1]

In order to prevent ingestion, bittering agent (denatonium benzoate) is usually added to engine coolant to make it taste unpleasant. In the United States, there is legislation before Congress (H.R.2567/S.1110) that would make the use of a bittering agent mandatory.

Propylene glycol

Food and Drug Administration (FDA) for use in food. However, propylene glycol-based antifreeze should not be considered safe for consumption. In the event of accidental ingestion, emergency medical services should be contacted.

Other developments

In the 1980s inventor Jack Evans discovered the advantages of using a waterless coolant. His final formulation is a mixture of ethylene glycol and propylene glycol. This coolant has a high boiling point of 188 °C (370 °F) and is not corrosive, solving many of water's problems including freezing.

Most commercial antifreeze formulations include dilution with water is usually used, resulting in a freezing point of approximately −40 °C. In warmer areas weaker dilutions are used.

Glycol antifreeze solutions should generally be replaced with fresh mixture every two years.{{{author}}}, {{{title}}}, [[{{{publisher}}}]], [[{{{date}}}]].

Organic acid technology

Certain cars are built with organic acid technology (OAT) antifreeze (e.g., [Dexcool http://www.acdelco.com.au/Assets/Dexcool%20-%20Specs.pdf]), which has an extended service life of five years or 150,000 miles^[2].

According to the Dexcool manufacturer, "mixing a 'green' coolant with DEX-COOL reduces the batch’s change interval to 2 years or 30,000 miles, but will otherwise cause no damage to the engine."^[3]

Dexcool specifically has caused controversy.^[4] It is casually linked with intake manifold gasket failures in GM's 3.1L and 3.4L and with other failures in 4.3L engines. A class action lawsuit is pending in Missouri to address some of these claims.

Typically OAT antifreeze contains a red or pink dye to differentiate it from the conventional inorganic coolants (blue or green). Some of the newer technology OAT coolants claim to be compatible with all types of OAT and inorganic-based coolants; these are typically green or yellow in color.

References

^ Keyes, Daniel C. (2005). Toxicity, Ethylene Glycol. eMedicine. Retrieved on 2007-02-13.
^ http://www.imcool.com/articles/antifreeze-coolant/Forward-dexcool2007.php
^ http://www.imcool.com/articles/antifreeze-coolant/dexcool-macs2001.php
^ http://www.imcool.com/articles/antifreeze-coolant/Forward-dexcool2007.php