kokpunktområder

Kokpunktområder, or boiling point ranges, describe the temperature interval over which a liquid mixture boils when exposed to a given pressure. For a pure substance, the boiling point at a specified pressure is a single temperature. For mixtures, different components begin to vaporize at different temperatures, so boiling occurs over a span. This span is often summarized by an initial boiling point and a final boiling point, or by the boiling-range distribution of a fraction.

In chemical engineering and refining, kokpunktområder are used to design separation processes such as distillation. The boiling range indicates which products can be obtained from a mixture at practical temperatures. Petroleum fractions, for example, are described by their boiling ranges, from light fractions to heavier residues. Boiling ranges can be affected by pressure: lowering pressure (vacuum distillation) generally shifts boiling to lower temperatures, enlarging practical kokpunktområder.

Measurement and data: boiling ranges are determined by distillation tests and by constructing boiling-point curves. In non-ideal mixtures, azeotropes or temperature-dependent composition can modify the effective range. The initial boiling point (IBP) is the temperature at which the first vapor appears, and the final boiling point (FBP) is where the liquid has largely ceased boiling. Understanding these ranges is essential for safe handling, storage, and process design in chemical industries.

See also: boiling point, distillation, azeotrope, phase diagram.