The carbon dioxide (called sometimes, in an unsuitable way “ carbonic gas ”) is a chemical Composé composed of a Atome of Carbone and two atoms of Oxygène and whose empirical formula is: CO2 .

This linear Molécule has as a developed formula of Lewis: O=C=O .

In the Normal conditions of temperature and pressure carbon dioxide is a Gaz colorless, odorless and with prickly savor commonly called carbonic gas or carbon dioxide.

It is present in the atmosphere in a proportion roughly equal to 0,0375% in volume, in this decade (years 2000), that is to say 375 PMV (left per million in volume). But it increases quickly, by approximately 2 ppmv/an, from the human activities of consumption of fossile fuels: coal, oil, gas.

It is a Gaz with greenhouse effect.

It is produced in particular at the time of the Fermentation Aérobie or of the made up Combustion of organics, and at the time of the Respiration of the living beings and the plants. For the latter, the Photosynthesis trap much more CO2 than its breathing does not produce any.

Physical characteristics

CO2 dissolved in water forms with it carbon Dioxide (H2CO3). It is more soluble in cool water than hot. The carbon dioxide is only moderately stable and it breaks up easily into HO and CO. On the other hand, when carbon dioxide dissolves in a basic aqueous solution (soda, potash…), the base déprotone carbon dioxide to form a Hydrogénocarbonate (HCO - ), also called Bicarbonate, then a Carbonate (CO 2 ). In this case, solubility is enormously increased. For example, an aqueous solution saturated with potassium carbonate (KCO) has a concentration of 112% (in mass) out of carbonate with 20°C.

History

Carbon dioxide was discovered about 1638 by a Belgian doctor of the name of Jan Baptist van Helmont which gave him the carbon dioxide name.

The properties of carbon dioxide were studied more in detail in 1750 per the chemist and British physicist, Joseph Black. About 1754, it called this gas fixed air, putting at evil the theory phlogiston still taught at that time.

The carbonic gas was thereafter isolated by English Pasteur Joseph Priestley in 1766.

In 1776, the French chemist Antoine-Laurent De Lavoisier highlighted that this gas is the product of the combustion of carbon with the Dioxygène. As of 1875 spread first artificially gas drinks thanks to the invention of the pressurized containers.

Uses

CO2 can be used for many things whose principal one is the extinction of fires. Many Datacenters (rooms of waiters of computers) or rooms of the files are equipped with a system which, in the event of fire, fills the room with CO2 what with like effect to extinguish fire. It is also used in Aquarophilie for a better growth of the plants It can also be used in liquid form (see low)

Liquid form

In liquid form, it is used like:
  • cooling for to freeze certain food,
  • cooling in the electronics industry,
  • agent of extinction in the Extinguishing S said “to carbon dioxide”, one sometimes speaks about dry ice because liquid CO2 is solidified immediately on the outlet side of the extinguisher by producing a white powder,
  • propellent agent (and sometimes also carbonating) for drinks been used for the pressure.

TO BE NOTED: with atmospheric pressure, carbon dioxide is never in liquid form. It passes directly from the solid form to the gas form (sublimation).

Form solid

Carbon dioxide in solid form or carbonic ice called also Dry ice or ice dries is resulting from liquid CO2 in the form of dry ice which is then compacted to become carbonic ice.

This carbonic ice is sublimated by not leaving any residue and very quickly produces a great quantity of cold (150 fr/h/kg with -78,5 °C), the man thus quickly found multiple uses to him.

  • in the form of " Pellets " (of the size of a grain of rice 3 mms diameter): primarily for cleaning and cryogenic scouring .

  • in " Stick " (stick of 16 mm): for the conservation, the transport of the products under controlled temperature (pharmaceutical product, transport of frozen, transport of samples etc).
  • in " Plate " or in " blocks " :
    • for the air supply (Catering), the delicatessens, undertaking etc
  • in " pains"
    • to make thick smoke (special effects, cinema, video).

Supercritical phase

Beyond its critical point, carbon dioxide enters a phase called " Supercritical ". The liquid curve of balance gas is stopped on the level of the critical point, ensuring the supercritical phase a continuum of the physicochemical properties without phase shift. It is a phase as dense as a liquid but ensuring of the properties of transport (viscosity, diffusion) near to a gas. Supercritical carbon dioxide is used as solvent " vert" , extracts being free from solvent trace.

  • decaffeinization of the coffee
  • treatment of the taste of the stopper in the cork stoppers
  • formatted of active ingredients micronized and in nanometric form
  • Extraction of chemical compounds or biological
  • purification of chemical compounds (mobile phase in Chromatography, in particular in HPLC)
  • for transport and storage at the time of the geological Sequestration of carbon dioxide (in rare industrial applications).

Reactivity

The electronegativity of the oxygen atoms makes very carbon central électrophile. Very many Nucléophile S can thus react with carbon dioxide but it should be noted that the product of the reaction is not inevitably stable. In general, one places dry ice in a closed container provided with a pipe; dry ice sublimates and one makes buller gas carbon dioxide in the reactional medium.

Some examples of reaction:

  • With a amine : one calls this reaction a Carbonatation. The product is an ammonium hydrogénocarbonate (R3N + CO2 + H2O → R3NH+HCO3-).
  • With a carbanion : one forms a Carboxylic acid after hydrolysis.
  • With water: to see above the introduction.

Tax CO2 on the polluting vehicles

An additional fee with the tax on the certificates of registration (Automobile license) is installation starting from July 1st, 2006 at the profit of the Agency of the environment and the control of energy (ADEME). It is calculated according to the CO2 rate emitted per kilometer since it exceeds 200 g/km or, in certain particular cases on the engine rating as soon as it is equal or higher than 10 CV.

This tax applies to all the particular vehicles (kind VP) put in circulation since June 1st, 2004.

Between 200 and 250 G/Km, each gram additional will cost you 2 € moreover. Beyond 250 G/Km, it will cost you 4 of them € per additional gram.

  • ex: if the vehicle has an issue rate of 234 g/km, then the tax rises with 2x34 = 68 €
  • ex: if the vehicle has an issue rate of 268 g/km (250 + 18), then the tax rises with: (50x2) + (18x4) = 172 €

If the vehicle were put in circulation after the June 1st, 2004 , the number of emitted grams figure in V7 of the automobile license.

For the vehicles which are not delivered EC, it is amount flat-rate which applies. The tax is then function of the number of CV of the vehicle:

  • if the number of horsepowers is lower than 10: no the tax due;
  • if the number of horsepowers lies between 10 and 15: amount due = 100 €;
  • if the number of horsepowers is higher than 15: amount due = 300 €.

See too

External bonds

  • Tax CO2 on the polluting vehicles

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