搜尋結果
0 (zero) is a number representing an empty quantity. Adding 0 to any number leaves that number unchanged. In mathematical terminology, 0 is the additive identity of the integers, rational numbers, real numbers, and complex numbers, as well as other algebraic structures. Multiplying any number by 0 has the result 0, and consequently, division ...
Viète. de Moivre. Euler. Fourier. v. t. e. In trigonometry, trigonometric identities are equalities that involve trigonometric functions and are true for every value of the occurring variables for which both sides of the equality are defined. Geometrically, these are identities involving certain functions of one or more angles.
Fortnite is an online video game and game platform developed by Epic Games and released in 2017.
- Production
- Uses
- Miscellaneous Chemical Reactions
- Toxicity
- Environmental Effects
- External Links
Industrial routes
Ethylene glycol is produced from ethylene (ethene), via the intermediate ethylene oxide. Ethylene oxide reacts with water to produce ethylene glycol according to the chemical equation: C2H4O + H2O → HO−CH2CH2−OH This reaction can be catalyzed by either acids or bases, or can occur at neutral pH under elevated temperatures. The highest yields of ethylene glycol occur at acidic or neutral pH with a large excess of water. Under these conditions, ethylene glycol yields of 90% can be achieved. The...
Biological routes
Ethylene glycol can be produced by recycling its polymeric derivatives such a polyethylene terephthalate.
Historical routes
According to most sources, French chemist Charles-Adolphe Wurtz (1817–1884) first prepared ethylene glycol in 1856. He first treated "ethylene iodide" (C2H4I2) with silver acetate and then hydrolyzed the resultant "ethylene diacetate" with potassium hydroxide. Wurtz named his new compound "glycol" because it shared qualities with both ethyl alcohol (with one hydroxyl group) and glycerin (with three hydroxyl groups). In 1859, Wurtz prepared ethylene glycol via the hydration of ethylene oxide....
Coolant and heat-transfer agent
The major use of ethylene glycol is as an antifreeze agent in the coolant in for example, automobiles and air-conditioning systems that either place the chiller or air handlers outside or must cool below the freezing temperature of water. In geothermal heating/cooling systems, ethylene glycol is the fluid that transports heat through the use of a geothermal heat pump. The ethylene glycol either gains energy from the source (lake, ocean, water well) or dissipates heat to the sink, depending on...
Anti-freeze
Pure ethylene glycol freezes at about −12 °C (10.4 °F) but, when mixed with water, the mixture freezes at a lower temperature. For example, a mixture of 60% ethylene glycol and 40% water freezes at −45 °C (−49 °F). Diethylene glycol behaves similarly. The freezing point depression of some mixtures can be explained as a colligative property of solutions but, in highly concentrated mixtures such as the example, deviations from ideal solution behavior are expected due to the influence of intermo...
Precursor to polymers
In the plastic industry, ethylene glycol is an important precursor to polyester fibers and resins. Polyethylene terephthalate, used to make plastic bottles for soft drinks, is prepared from ethylene glycol.
Silicon dioxide dissolves slowly in hot ethylene glycol in the presence of alkali metalbase to produce silicates.
Ethylene glycol has relatively high mammalian toxicity when ingested, roughly on par with methanol, with an oral LDLo = 786 mg/kg for humans. The major danger is due to its sweet taste, which can attract children and animals. Upon ingestion, ethylene glycol is oxidized to glycolic acid, which is, in turn, oxidized to oxalic acid, which is toxic. It...
Ethylene glycol is a high-production-volume chemical. It breaks down in air in about 10 days and in water or soil in a few weeks. It enters the environment through the dispersal of ethylene glycol-containing products, especially at airports, where it is used in de-icing agents for runways and airplanes. While prolonged low doses of ethylene glycol ...
The slash is a slanting line punctuation mark /. It is also known as a stroke, a solidus, a forward slash and several other historical or technical names. Once used to mark periods and commas, the slash is now used to represent division and fractions, exclusive 'or' and inclusive 'or', and as a date separator.
In linear algebra, an eigenvector (/ ˈaɪɡən -/ EYE-gən-) or characteristic vector is a vector that has its direction unchanged by a given linear transformation. More precisely, an eigenvector, , of a linear transformation, , is scaled by a constant factor, , when the linear transformation is applied to it: .
In astronomy, dark matter is a hypothetical form of matter that does not interact with light or other electromagnetic radiation. Dark matter is implied by gravitational effects which cannot be explained by general relativity unless more matter is present than can be observed.
