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A fractionating column or fractional column is equipment used in the distillation of liquid mixtures to separate the mixture into its component parts, or fractions, based on their differences in volatility. Fractionating columns are used in small-scale laboratory distillations as well as large-scale industrial distillations.
Fractionation makes it possible to isolate more than two components in a mixture in a single run. This property sets it apart from other separation techniques. Fractionation is widely employed in many branches of science and technology. Mixtures of liquids and gasses are separated by fractional distillation by difference in boiling point.
The apparatus is assembled as in the diagram. (The diagram represents a batch apparatus as opposed to a continuous apparatus.) The mixture is put into the round-bottomed flask along with a few anti-bumping granules (or a Teflon-coated magnetic stirrer bar if using magnetic stirring), and the fractionating column is fitted into the top. The ...
The typical McCabe–Thiele diagram in Figure 1 uses a q-line representing a partially vaporized feed. Example q-line slopes are presented in Figure 2. The number of steps between the operating lines and the equilibrium line represents the number of theoretical plates (or equilibrium stages) required for the distillation.
A fraction in chemistry is a quantity collected from a batch of a substance in a fractionating separation process. In such a process, a mixture is separated into fractions, which have compositions that vary according to a gradient. A fraction can be defined as a group of chemicals that have similar boiling points.
Another example of vapor and liquid contact devices are the spikes in laboratory Vigreux fractionating columns. The trays or plates used in industrial distillation columns are fabricated of circular steel plates and usually installed inside the column at intervals of about 60 to 75 cm (24 to 30 inches) up the height of the column.
Spinning band distillation takes this concept one step further by using a spinning helical band made of an inert material such as metal or Teflon to push the rising vapors and descending condensate to the sides of the column, coming into close contact with each other. This speeds up equilibration and provides for a greater number of ...
This technique is frequently employed in chemical synthesis; in this case, the component of the still responsible for the separation is a fractionating column. A continuous still can, as its name suggests, sustain a constant process of distillation.