As the value of increases above 1, separation by distillation becomes progressively easier. When the volatilities of both key components are equal, it follows that = 1 and separation of the two by distillation would be impossible under the given conditions. That means that ≥ 1 since the larger value of the more volatile component is in the numerator and the smaller of the less volatile component is in the denominator. Thus, a value (= ) for a more volatile component is larger than a value for a less volatile component. When their liquid concentrations are equal, more volatile components have higher vapor pressures than less volatile components. = commonly called the K value or vapor-liquid distribution ratio of a component = the vapor-liquid equilibrium concentration of component in the liquid phase = the vapor-liquid equilibrium concentration of component in the vapor phase = the relative volatility of the more volatile component to the less volatile component Schematic diagram of a large-scale binary distillation column.įor a liquid mixture of two components (called a binary mixture) at a given temperature and pressure, the relative volatility is defined as

Relative volatilities are not used in separation or absorption processes that involve components that chemically react with each other (for example, the absorption of gaseous carbon dioxide in aqueous solutions of sodium hydroxide which yields sodium carbonate). Relative volatilities are used in the design of all types of distillation processes as well as other separation or absorption processes that involve the contacting of vapor and liquid phases in a series of equilibrium stages. By convention, relative volatility is typically denoted as. In other words, the higher is the relative volatility of a liquid mixture, the easier it is to separate the mixture components by distillation. In effect, it indicates the ease or difficulty of using distillation to separate the more volatile components from the less volatile components in a mixture. This measure is widely used in designing large industrial distillation processes. Relative volatility is a measure of the difference between the vapor pressure of the more volatile components of a liquid mixture and the vapor pressure of the less volatile components of the mixture. For other uses of the term Volatility, please see Volatility (disambiguation). This article is about Relative volatility.

Hydrocarbon depriester chart