DeanStarklaitteella

Dean-Starklaitteella, or the Dean–Stark method, is a laboratory distillation technique used to determine the water content of a sample by azeotropic distillation with an immiscible organic solvent. It is widely applied in industries such as fats and oils, polymers, and resins to assess moisture or extractable water in materials that contain solids or oils.

The principle relies on heating a sample with an appropriate solvent that forms an azeotrope with water and is immiscible with water. As distillation proceeds, the water co-distills with the solvent and is separated in a special Dean-Stark receiver, where the water accumulates in a calibrated trap while the organic solvent returns to the reaction flask. Over time, water collects in the trap until the desired endpoint is reached. The amount of water is read from the calibrated receiver and converted to a moisture percentage by reference to the initial sample mass.

Typical procedure involves weighing a known amount of sample into the flask, adding solvent, and assembling the Dean-Stark apparatus. The mixture is heated to reflux, and the distillate passes through the condenser into the trap. When the desired amount of water has been collected, the apparatus is cooled, and the water readout is used to calculate moisture content. Common solvents include toluene, xylene, and chlorobenzene, chosen for their good azeotrope formation with water and their immiscibility with water.

Advantages of the method include direct measurement of moisture in samples with solids or oils and the avoidance of chemical titrants. Limitations include dependence on suitable solvent choice, potential inaccuracies with emulsions or reactive samples, and longer analysis times compared with some rapid techniques.