The solvent in Chemistry is one of the components of a solution, generally the one present in greater quantity or the one that, in the pure state, is in the same state of aggregation as the solution. Also, any substance capable of dissolving another, generally without altering its chemical nature.
Commonly the solvent they are liquids, in normal conditions of temperature and pressure; in several cases, however, they act as solvent also metals or molten salts or even liquefied gases; water represents the solvent more common (it is sometimes called the universal solvent because it is capable of dissolving numerous substances), but many other compounds are widely used (solvent non-aqueous).
The solubility of a solute in one solvent depends on the chemical nature of both, on the temperature, on the pressure, etc. in many cases, it occurs that a compound dissolves in preference to those substances which have functional groups, structural similarities, etc. in common with it; thus, water dissolves alcohols and many carbon hydrates, compounds which contain −OH groups; hydrocarbons dissolve many constituents of petroleum, etc.
In some cases, the SOLVENT causes the ionization of the solute (ionizing solvent).
Solvents used industrially; they belong to practically all classes of known chemical compounds: hydrocarbons (petroleum fractions, terpenes, hydronaphthalene, etc.), alcohols (methyl, ethyl, butyl, propyl, glycols, glycerin, etc.), phenols, ethers, aldehydes, ketones, esters, chloro derivatives, nitrogen compounds, sulfurates, etc. Among the inorganic liquids, they act as solvent carbon sulfide, halogenated derivatives of phosphorus, etc.
The solvent’s essential characteristics, on which the selection criteria in the applications are essentially based, are vapor pressure, boiling temperature, the heat of vaporization, flammability, immiscibility with other liquids, explosiveness, and toxicity.
Among the numerous fields of application of the various classes of solvent, the most important are the industry of paints, adhesives, textile fibers,
Industrial production, booming throughout the world, reached in the 2000s 5 million tons per year. The tremendous demand comes from the paint and coating materials industry.
The consumption of solvent is also on the rise. Solvents are used to purify products in the pharmaceutical industry and for extraction processes in the food industry.
As the solvent demand, however, there is an increasingly felt need to protect operators’ health and safeguard the environment. It stimulated the search for solvent with less impact on health and the environment.
In paints industries, alternative systems to traditional technology based on polymers diluted in organic solvents (on average, a part of solvent for a portion of polymer) are increasing interest.
Thus, in addition to systems that tend to decrease, the solvent ratio. / Polymer or to replace the solvent organic with water, technology (called radiation curing) is also gaining ground, adopting formulations utterly free of solvent. The monomers, with the addition of suitable photoinitiators, are cross-linked on-site by irradiation with ultraviolet radiation.
Solvate: a complex consisting of the molecules or ions of the solute, which are associated with a certain number of molecules of solvent partly changing their characteristics and their behavior (the solute particles change their size, their mobility, and reactivity, etc.).
Between solvent and solute interactions of different types occur according to the cases, going from those of an electrostatic nature (e.g., dipole-dipole), to hydrogen bonds, to real chemical bonds, with the formation of coordination compound solvent.
Solvolysis Reaction occurs between a solute (neutral ion or molecule) and the solvent, leading to the formation of neutral or electrically charged product solvent.
Solvolysis reactions take different names according to the solvent (hydrolysis, alcoholysis, ammonolysis, depending on whether it is water, alcohol, ammonia).
Solvolysis often occurs in solvent polar, be they acidic (hydrofluoric acid, acetic, hydrocyanic, etc.), amphoteric (water), or essential (ammonia, pyridine, hydrazine, etc.); the resulting solution after solvolysis may have a more acidic or more basic character than that of solvent.
If the solvolysis products and the solute are all soluble in the solvent, an equilibrium is established between them. In contrast, if one of the solvolysis outcomes is a gas or an insoluble substance in the solvent, then the reaction proceeds irreversibly towards the formation of this product.