Ferroin

Ferroin is an inorganic compound used as an indicator in oxidation-reduction (redox) titrations because of its distinct color change. It is a complex of ferrous ion (Fe^2+) with 1,10-phenanthroline, an aromatic heterocyclic compound. The chemical formula for ferroin is typically represented as C_{12}H_{8}N_{2}·Fe^2+. In its oxidized form, ferroin changes to a pale blue color, making it easy to determine the endpoint of a titration.

Properties and Usage

Ferroin exhibits a clear color change from red to pale blue upon oxidation, which is reversible upon reduction. This property makes it particularly useful in the laboratory for determining the endpoint of redox titrations. The transition occurs over a narrow pH range, making ferroin an excellent indicator for a variety of redox reactions.

Preparation

Ferroin is prepared by mixing solutions of 1,10-phenanthroline and ferrous sulfate. The reaction that occurs forms the ferroin complex, which can be used directly in titration experiments.

Applications

In addition to its use as a redox indicator, ferroin has applications in biochemistry and molecular biology, particularly in the study of DNA where it can be used to quantify the amount of DNA present in a sample. Its ability to intercalate into DNA makes it a useful tool for researchers.

Safety

Handling ferroin requires standard laboratory precautions. It should be kept away from strong oxidizing agents to prevent its oxidation to the ferric form, which is not useful as an indicator.