Soxhlet Extraction of Coffee

Coffee components are extracted into water through specially designed

glassware.

Purpose

This simple experiment shows how a natural products are often extracted to concentrate soluble materials. A soxhlet extractor is specially designed for such extractions.

Demonstration

This experiment shows the glassware setup required for a soxhlet extraction. Coffee is placed in the extraction “thimble”

The experiment shows how vaporization and condensation occur throughout the apparatus.

Concepts

Extraction

Changes of State

Solubility

Extraction

Extractions are used when we want to separate substances. One way this can be done is by using a solvent in which a desired substance dissolves in and the undesired substance does not dissolve in. Coffee flavor from coffee grounds is a great example, as we leave behind the coffee grounds and obtain a great flavored morning beverage.

Changes of State

Evaporation-the phenomenon in which liquid molecules have enough energy to convert

to the gaseous state without boiling

-evaporation can occur at nearly any temperature: at any time some of the molecules in a liquid will have enough energy to escape into the air

Condensation-the phenomenon in which gas molecules lose energy required to be a gas

and collect on a cool surface as a liquid

-example, on a hot, humid summer day water condenses on the outside of a glass of ice water

When molecules have lower energy their intermolecular attractions take hold

SolubilitySolubility is a function of how well a substance

dissolves in a solvent.Coffee grounds are insoluble in water (nothing

dissolves)However, the flavorings in the coffee grounds are

soluble in water (large amounts dissolve)—they are said to be the solute in the solution

In this demonstration, the soluble flavorings are what we want in our water.

Coffee is a solution: solutions include a solute (substance being dissolved) and a solvent (substance doing the dissolving)

Conclusions

Using a soxhlet extractor is a way to separate soluble material from insoluble material

A soxhlet extractor repeatedly extracts with fresh solvent until it is stopped. Thus, it is possible to extract all of the soluble material, if given enough time. This would make for really strong coffee in this demonstration!

Comments

A soxhlet extraction is commonly used to extract compounds from plants to discover active compounds such as natural pharmaceuticals

Compounds extracted from plants or animal material are commonly called natural products

Some natural products are very useful chemical species for the production of drugs and ointments