Antifreeze: Difference between revisions
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==Agents== |
==Agents== |
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===Methanol=== |
===Methanol=== |
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Methanol, also known as methyl alcohol, carbinol, wood alcohol, wood naphtha or wood spirits, is a chemical compound with chemical formula CH3OH (often abbreviated MeOH). It is the simplest alcohol, and is a light, volatile, colourless, flammable, poisonous liquid with a distinctive odor that is somewhat milder and sweeter than ethanol (ethyl alcohol). At room temperature it is a polar liquid and is used as an antifreeze, solvent, fuel, and as a denaturant for ethyl alcohol. It is also used for producing biodiesel via transesterification reaction. |
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methanol is a alchol with one carbon in a carbon chain. there are three hydrogyn molecules connected to the single carbon chain, also a OH is connected to the carbon molecule. in total a cabon molecule can only connect to 4 other molecule bonds. methanol is alcohol from wood. ehtanol is alcohol from friuts or vegetables. methanol is a highly poisonous liquid. so do not mistake it as typical alcohol. |
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===Ethylene glycol=== |
===Ethylene glycol=== |
Revision as of 21:24, 10 January 2008
Antifreeze is used in internal combustion engines, and for many other heat transfer applications, such as electronics cooling and chillers for HVAC. Compounds are added to water to reduce the freezing point of the mixture to below the lowest temperature that the system is likely to be exposed to, and to inhibit corrosion in cooling systems which often contain a range of electrochemically incompatible metals (aluminum, cast iron, copper, lead solder, etc.). The term "colligative agent" is to be preferred as, in warm climates, the benefit of these compounds is to increase the 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
Methanol, also known as methyl alcohol, carbinol, wood alcohol, wood naphtha or wood spirits, is a chemical compound with chemical formula CH3OH (often abbreviated MeOH). It is the simplest alcohol, and is a light, volatile, colourless, flammable, poisonous liquid with a distinctive odor that is somewhat milder and sweeter than ethanol (ethyl alcohol). At room temperature it is a polar liquid and is used as an antifreeze, solvent, fuel, and as a denaturant for ethyl alcohol. It is also used for producing biodiesel via transesterification reaction.
Ethylene glycol
![](http://upload.wikimedia.org/wikipedia/commons/thumb/2/28/Ethylene_glycol_chemical_structure.png/100px-Ethylene_glycol_chemical_structure.png)
Ethylene glycol solutions became available in 1927 and were marketed as "permanent antifreeze", since the higher boiling points provided advantages for summertime use as well as during cold weather. They are still used today. Ethylene glycol antifreezes are poisonous and should be kept away from any person or animal (children and especially dogs) that might be tempted by its sweet taste. They form 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, ethanol (alcoholic beverages) can be administered until proper treatment can be started in order to slow the conversion of methanol to formaldehyde and formic acid which are the substances responsible for methanol's toxicity. In practice, ethanol can be administered intravenously by doctors to counter ethylene glycol and methanol poisoning, but now that another antidote is available (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
![](http://upload.wikimedia.org/wikipedia/commons/thumb/3/3e/Propylene_glycol_chemical_structure.png/100px-Propylene_glycol_chemical_structure.png)
Propylene glycol, on the other hand, is considerably less toxic and may be labeled as "non-toxic antifreeze". It is used as antifreeze where ethylene glycol would be inappropriate, such as in food-processing systems or in pipes in homes, as well as numerous other settings. It is also used in food, medicines, and cosmetics, often as a binding agent. Propylene glycol is "generally recognized as safe" by the 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 corrosion inhibiting compounds, and a colored dye (commonly a green, red or blue fluorescent) to aid in identification. A 1:1 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. {{citation}}
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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 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
Further reading
- ATSDR - Case Studies in Environmental Medicine: Ethylene Glycol and Propylene Glycol Toxicity U.S. Department of Health and Human Services (public domain)
- Antifreeze Poisoning
- Slate.com: Why is antifreeze so delicious?
- GM Owners Still Steaming Over Dex-Cool
- Engine Coolant Change Information & Procedure