A solvent is a liquid which with the property to dissolve and dilute other substances without modifying them chemically and itself to change. Water is the solvent more running.

General information

The organic term solvent refers to the solvents which are made up organics which contain Atome S of Carbone. Usually, the solvents have a low Melting point and evaporate easily. The solvents make it possible to dissolve the reagents and to lead the reagents to touch itself. They do not react chemically with the compound dissolves: they are inert. The solvents can also be used to extract the soluble compounds from a mixture, the most common example being the infusion of The in warm water. The solvents are often transparent liquids with a characteristic odor. The concentration of a solution is the quantity of compound dissolved in a certain volume of solvent.

For the liquid solutions (liquid uniform phase containing several chemical species), if one of the species is very largely majority (at least a factor 100), one calls it the solvent . It is the case of water for the aqueous solutions (for example an aqueous solution of Copper sulfate: water is the solvent and the ions sulfates and coppers (II) the Soluté S).

In general, the atoms or molecules of comparable nature are assembled to form a Liquide or a solid (a Cristal or an amorphous solid). In the case of a solution, the solvent prevents the atoms or molecules to be assembled, it disperses them. In the case of water, that occurs according to two phenomena:

  • a reduction in the interaction electric (forces of Van der Waals): water has a electric Permittivité from approximately 80, which means that it divides the forces of Coulomb by eighty;
  • a Solvation (for water a Hydration): if the molecules of solvent are polar, they can surround the dissolved species and form a “shield”.

Types of solvents

One distinguishes 3 types of solvents:

  • the protic solvents ''' ''' (also called solvents protogenes): having one or more hydrogen atoms suitable for form hydrogen bonds. For example, the Water, the Methanol, the ethanol, etc

  • the polar aprotic solvents ''' ''': having a Dipole moment not no one and stripped of hydrogen atoms suitable for form hydrogen bonds. For example, acétonitrile (CH3CN), the diméthylesulfoxyde (DMSO, (CH3) 2SO), the Tétrahydrofurane (THF, C4H8O), etc

  • the non-polar solvents ''' aprotic ''': having a Dipole moment permanent no one. For example, the Benzene, hydrocarbons: Alkane cyclic S ramified or linear, alkanes, Olefinic hydrocarbon S, etc

Acid dissolution

Dissolution can be done by chemical reaction between species of solvent (in general of the Ion S) and the solid. The most frequent case is that of dissolution by a Acide: the Proton S H+ (or in the Water, the ions oxonium or hydronium H3O+) cause a Oxydation solid

2M + 2:00 + → 2M+ + H2
(the atom of solid M yields a electron to the ion H+ which can then form a molecule of Dihydrogène), the ion M+ being then soluble in solvent.

Dissolution in glass

At high temperature (beyond 2  000  °C), the Verre (Silica or Oxide of Silicon SiO2) is liquid. One can thus dissolve there a certain number of products which are, them, solids at this temperature.

One can also dissolve the solids in other types of glass, such as for example the méta borate of Lithium the lithium or tetraborate, used to dilute materials to analyze in Spectrométrie of x-ray fluorescence (technique of preparation known as of the “molten Perle”).

Although taking place at high temperature and with a different solvent, the principle is similar to dissolution in water (dispêrsionl solvation, acid dissolution).

Ionic solvents

Whereas the majority of solvents are molecular natures (made of only one neutral species), there exists a new solvent class, called liquid ionic , composed of Anion S and Cation ionic liquid S. the are molten salts having a Point melting lower than 100°C and an almost null vapor tension (they are not-volatile). They constitute an increasingly serious alternative to traditional molecular solvents and right now are very much used in electrochemistry. Many current research is interested in their use for separation of metals radioactive S and could lead to solutions particuliairement ecological for the reprocessing of the nuclear waste.

Examples of solvents

The Eau is the most known solvent.

Various types of solvents:

Uses

The solvents are often used as thinners, for example in Peinture.

Certain solvents are used as grease-removers, as for example the Perchloroéthylène which is used for the dry Nettoyage

Dangers of solvents

Many solvents present health risks, which is all the more worrying as in 2003 14,7% of the paid population was exposed to solvents (against 12,3% in 1994; studies INRS); it is not necessary to work in a chemical plant to be exposed there: it is also the case of the painters, the plasturgie, printing works, cleaning, funerary, the laundry, etc

Several types of ethers of glycol were thus blamed in cases of Cancer S low registers; nine were classified " reprotoxiques" (dangerous for the fetuses of the expectant mothers).

Lastly, of many chemical compounds were the subject of weak studies before their marketing and their effects and real risks are badly known. From where passions around the European project REACH which could oblige the industrialists has to test better more products, and the importance of the work of the committees of hygiene (CHSCT in France) on these questions within the framework of work. The air of the dwellings can also conceal many solvents (resulting from the adhesives, painting, even of the maintenance products), from where the recommendation to air each part at least 10 minutes each day.

See too

External bonds

  • Table with the parameters of solubility of HILDEBRAND of usual solvents

Simple: Solvent

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