The solvent is the substance that dissolves the solute and the component of a chemical solution present in the greatest amount. While most common solvent are liquids, a solvent can be a solid or gas. The word “solvent” comes from the Latin word “solvō,” which means “to loosen or solve.” Solvents are important in chemistry, biology, pharmaceuticals, and industrial applications.
The most common solvent is water, but we encounter many other solvents in daily life. This table identifies the solvent in familiar solutions:
|Nail polish||Liquid||Ethyl acetate or butyl acetate|
|Nail polish remover||Liquid||Usually acetone|
|Oil paint||Liquid||Turpentine or white spirits|
How to Tell If a Solvent Will Dissolve a Solute
Whether or not a solute will dissolve in a solvent depends on its solubility. Solubility, in turn, depends on temperature, pressure, and the presence of other other chemicals in a mixture. For example, consider table salt (sodium chloride) as a solute. Table salt is much more soluble in hot water than it is in cold water (water is the solvent).
It is much less soluble in certain other solvents, such as methanol or vegetable oil. Why? Whether a solute is soluble in a solvent depends on the polarity of the compounds. Remember, “like dissolves like.” What this means is that a polar solute (like salt) usually dissolves in a polar solvent (like water) but not in a nonpolar solvent, like oil. A nonpolar solute (like the wax) tends to dissolve in a nonpolar solvent (like xylene). Often, molecules with both nonpolar and polar portions (like ethanol and acetone), may dissolve or be dissolved by both polar and nonpolar compounds.
Protic and Aprotic Solvents
Polar solvents may be classified as protic or aprotic. Protic solvents readily dissolve anionic solutes (negatively-charged solute) by hydrogen bonding. Water is an example of a protic solvent. Aprotic solvents have large dipole moments (large separation of positive and negative charges in the molecule). Usually, the negative part of an aprotic solvent dissolves cationic or positively-charged solutes. Examples of aprotic solvents in acetone and dichlorobenzene.
While the scientific definition of a solvent is a chemical that dissolves a solute, it almost always refers to an organic compound in most industries. In this usage, many solvents present health hazards and some are flammable. Examples of common industrial solvents include:
- Diethyl ether
- Acetic acid
- Hansen, C.M. (January 2002). Hansen Solubility Parameters: A User’s Handbook. CRC press. ISBN 978-0-8493-7248-3.
- Lowery, T.H.; Richardson, K.S. (1987). Mechanism and Theory in Organic Chemistry (3rd ed.). Harper Collins Publishers. ISBN 978-0-06-364044-3.
- Tinoco, I.; Sauer, K,; Wang, J.C. (2002). Physical Chemistry. Prentice ISBN 978-0-13-026607-1.