Editing Boiling point (section)

==Impurities and mixtures==
In the preceding section, boiling points of pure compounds were covered.  Vapor pressures and boiling points of substances can be affected by the presence of dissolved impurities ([[solutes]]) or other miscible compounds, the degree of effect depending on the concentration of the impurities or other compounds.  The presence of non-volatile impurities such as [[Salt (chemistry)|salts]] or compounds of a [[Volatility (chemistry)|volatility]] far lower than the main component compound decreases its [[mole fraction]] and the [[Solution (chemistry)|solution]]'s volatility, and thus raises the normal boiling point in proportion to the [[concentration]] of the solutes.  This effect is called '''[[boiling point elevation]]'''.  As a common example, [[Saline water|salt water]] boils at a higher temperature than pure water.

In other mixtures of miscible compounds (components), there may be two or more components of varying volatility, each having its own pure component boiling point at any given pressure.  The presence of other volatile components in a mixture affects the vapor pressures and thus boiling points and [[dew point]]s of all the components in the mixture. The dew point is a temperature at which a vapor [[Condensation|condenses]] into a liquid. Furthermore, at any given temperature, the composition of the vapor is different from the composition of the liquid in most such cases.  In order to illustrate these effects between the volatile components in a mixture, a '''boiling point diagram''' is commonly used. [[Distillation]] is a process of boiling and [usually] condensation which takes advantage of these differences in composition between liquid and vapor phases.