Alizarin red

Alizarin Red is an organic compound that is used as a dye, primarily for coloring fabrics and in the preparation of lake pigments. It is derived from the root of the madder plant, and was historically the first natural dye to be synthesized from coal tar.

History

Alizarin Red was first used as a dye in the Middle East and Asia more than 3,000 years ago. The madder plant was cultivated for its roots, which were boiled in water to extract the dye. The process was labor-intensive and the color of the dye varied depending on the age of the plant and the method of extraction.

In the 19th century, chemists discovered that Alizarin Red could be synthesized from anthraquinone, a compound found in coal tar. This discovery led to the industrial production of Alizarin Red and the decline of the madder industry.

Properties and Uses

Alizarin Red is a red crystalline solid that is insoluble in water but soluble in alcohol and ether. It is used as a dye for fabrics and leather, and in the preparation of lake pigments for paints and printing inks.

In addition to its use as a dye, Alizarin Red is used in the laboratory as a pH indicator, changing color from yellow to red as the pH decreases. It is also used in biological research to stain calcified tissues, such as bone and cartilage.

Health and Safety

Exposure to Alizarin Red can cause skin and eye irritation, and prolonged exposure can lead to more serious health effects. It is classified as a possible human carcinogen by the International Agency for Research on Cancer.

See Also

• Anthraquinone
• Madder plant
• Lake pigments
• International Agency for Research on Cancer