Solvents are any liquids that can dissolve other substances. Common solvents include water, ethanol, acetone, and petroleum distillates such as gasoline and diesel fuel.
Dilute solvents generally have low boiling points because the large number of molecules in the liquid reduce the attractive forces (the adhesion between particles) in the liquid. When a solvent is diluted by adding more solute (e.g., a sugar solution), these attractions are reduced faster than when it is diluted by adding more solvent to an already-diluted mixture (e.g., water). A high percentage of dissolved molecules will make one of these solutions less viscous or "runnier.”
Solvent types differ in their miscibility with water. Alcohol, glycol, and xylene are miscible in water but hydrocarbon-based solvents are not. For example, dissolving alcohol in water produces a mixture of just alcohol and water (no third phase), because both alcohol and water are aqueous solutions at the same temperature, while the two do not mix when hot (see Raoult's law). This allows for easy separation of coexisting phases (e.g., immiscible liquid and gas or solid) by putting the mixture into a separatory funnel or decanter. Solvent dissolves nonpolar solvent more readily than it does polar solvent. In the latter case, it is called an emulsifier.
Solvents are used in the manufacture of many useful materials such as plastics (e.g., polyvinyl chloride), dyes, pharmaceuticals (e.g., as solvents, vehicle or diluent), detergents (e.g., diethylene glycol monoethyl ether acetate aka DMDGA), perfumes (e.g., balsam of peru), peroxide cleaners (especially under water pressure), and home and industrial cleaners. They are also used to remove glue, stains from porous materials, or any other adhering substance and can be used to dissolve some types of paints (e.g., lacquer) and coatings. Solvents of low volatility are non-flammable but solvent blends are flammable.
Early chemical studies of the solubility of various substances in water were performed around 1600 by Johann Juncke and Robert Boyle. Solvents can act as a method of analysis that enables a sample to be separated into its components, some fraction is extracted into the solvent, which carries its constituents with it (extraction). There are several methods for analyzing a sample using solvents.
The industry produces tens of thousands of different products, with diverse end-uses including paints, varnishes, cleaners for hard and soft surfaces, such as kitchen worktops or shower enclosures. These products can be used to serve industrial markets (e.g., coatings) as well as domestic ones (e.g., detergents). Solvents are typically organic compounds that possess few nitro groups so they are not explosive like nitroglycerin but still contain oxygen molecules that help them dissolve other substances such as fats or oils.
The chlorinated solvents industry is an important branch of the solvent industry. Many of its key components are created by electrophilic aromatic substitution reaction of phenols and anilines with chlorinated hydrocarbons in the presence of such additives as light metals or other compounds. The resulting product can be used as a cleaning agent for metals, wood, and fabrics. The raw materials used in the production of chlorinated solvents are common organochlorine compounds (vinyl chloride, vinylidene chloride etc.). Some products from this sector are methylene chloride (CHCl), trichloroethylene (CHClCCl), and tetrachloroethylene (CHClCCl).
The solvents industry is the world’s third largest chemical production sector, and the largest in Europe.