Alizarin is a chemical compound found naturally in the roots of some species in the madder family, and produced synthetically from an anthraquinone base. In pure form, alizarin is reddish-orange and can be used as a pigment or dye for a wide variety of projects. It is famous for being very color-fast and visually bold and has been used by a number of human civilizations in arts and crafts, as well as in the production of fabrics for uniforms and other wear. The compound is referenced in the name of alazarin crimson, a color historically made with this compound.
One madder species, Rubia tinctorum or dye madder, has high concentrations of this compound in its roots. A number of early human societies in regions like Egypt and India used madder in the production of dyes for clothing, as well as pigments for paint. Alizarin was the famous red used in the production of military uniforms for England in the 18th century, and was also used in the production of French army uniforms.
In the 1800s, chemists figured out how to stabilize madder and make it a longer lasting, more colorfast dye. This was followed in the late 1860s by the development of a synthetic version of alizarin. Synthesizing the chemical compound allowed people to produce red and orange dyes for a fraction of their former cost and led to a precipitous decline in the value of madder, as it was possible to produce dyes and pigments much more cheaply and quickly with synthetic alizarin. This compound was the first natural plant dye to be synthesized and it was followed by many others.
One use for alizarin that persists to this day is in the preparation of stains for chemistry and biology. The red dye highlights structures of interest and can be used in tests where stains are necessary to identify specific organisms or other things of concern in a sample. Synthetic dyes are usually used for stains today, as they are more stable, reliable, and affordable for lab use.
It is still possible to find alizarin-based dyes made with madder, rather than synthetics. Some crafters are interested in working with natural plant dyes and may harvest, process, and stabilize their own dyes to make them more durable and colorfast. Craft stores occasionally sell plant dyes commercially packaged for use by people interested in dying, but lacking the skills and facilities to prepare their dyes at home or in the workshop.