What to extract

For tea infusions, the herb is poured with boiling water or placed in hot water. When the tea is left to steep, the ingredients of the tea herb dissolve in the water. The drinkable tea is the watery extract of the herb. The residue remains in the tea strainer after sieving.

Let the tea steep in the cup

In the extraction a substance is separated from a liquid, from a solid or from a gas with a solvent. The solvent is also called extraction agent and is suitable if it dissolves the substance to be extracted but not the other components. The mixture of extracted substance and solvent is called extract, the remaining residue Raffinate.

In the Maceration a substance is immersed in a liquid such as water, alcohol or oil for a certain period of time. The product with the liquid and the dissolved substance is called Macerate, in pharmacy this is also known as "Cold infusion". The process is used in the manufacture of medicines from medicinal plants. High-proof alcoholic beverages with flavorings are also produced in this way.

Alcohol maceration of marigolds

In the Percolation one lets water or alcohols flow through a solid substance. The process is mainly used for the extraction of active plant substances in the pharmaceutical industry. But it is also commonplace in every household: During the preparation of coffee, the aromas are percolated from the ground coffee by hot water.

Percolation for the extraction of herbal active ingredients

At the Digest a substance is intensively mixed with a liquid by stirring. You wait until the insoluble components have settled on the bottom and then decant the liquid with the extracted substance. In pharmacy one also speaks of one Vortex extraction.

Vortex extraction of marigold with agitator

At the Shake out, liquid-liquid extraction, you add a solvent such as gasoline, which does not mix with the original solution, to an already existing solution or to an emulsion such as milk. If you add gasoline to milk, it initially floats on top of the milk due to its lower density. After shaking vigorously, some of the milk fat has passed into the gasoline. The two liquids with different densities are then separated using a separating funnel. After the fatty gasoline has evaporated on a slide, a grease stain remains.

At the Leaching a solid is extracted from a solid mixture with the aid of a solvent. If you have a mixture of sand and table salt, the table salt can be dissolved by adding water while the sand settles on the ground. The process is mainly used in the extraction of vegetable dyes (> description of the experiment) or metals from ores.

At the Boil out For example, linseed containing linseed oil is heated to boiling with gasoline. Due to the high temperature, the linseed oil is extracted better than in the cold solvent. It dissolves in gasoline and can be obtained in pure form by evaporating the gasoline (> description of the experiment). Another well-known example from everyday life is making tea.


An apparatus used very frequently in the laboratory for the extraction of solids is the Soxhlet extraction apparatus. The solvent is poured into the round-bottomed flask and the mixture to be extracted is put into the extraction thimble. When the solvent is heated in the round bottom flask, it evaporates, rises up the side tube and condenses in the reflux condenser. The condensed and still hot solvent drips into the extraction thimble. The extract rises to the maximum height of the siphon, through which it then flows back into the round-bottomed flask. The solvent evaporates again. The Soxhlet apparatus enables a continuous and very productive extraction that can take many hours.

Soxhlet extraction apparatus

When extracting gases, the gas mixture to be extracted is passed through a gas washing bottle filled with a solvent. For example, if air is passed through caustic soda, carbon dioxide is absorbed (> drying and> absorbing).

Master copies to be extracted