To dye for

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A dye is a chemical compound capable of imparting color to a substance to which it is applied.

For millennia, humans have used dyes to color all kinds of objects. Humans first used dyes to paint pictures on the walls of caves and later to dye cloth for clothing and decoration.

Before the advent of synthetic dyes, the only colorants available were natural dyes. Natural dyes are derived from certain plants, invertebrate animals or minerals. The majority of natural dyes are vegetable dyes that are derived from specific plant parts such as roots, berries, bark, leaves or wood.

For example, the logwood tree was once an important source of black dye. It was obtained from the blood-red heartwood of the tree, and is still used today as a source for the widely used biological stain hematoxylin.

Synthetic dyes are sometimes referred to as "coal tar dyes" since they are manufactured from substances which, until recently, were only obtained from coal tar.

In 1856, the first commercially successful dye, mauveine, was accidentally discovered by a British chemist. He was trying to make an artificial form of quinine that could be used to treat malaria. The introduction of mauveine triggered the decline in the dominance of natural dyes in world markets.

Today, more than 700 synthetic dyes are now in daily use to color all kinds of products.

Various synthetic dyes are also important in medical procedures and research. For example, they are used to stain tissues in pathology work, as test reagents, as therapeutic agents, as tracers in diagnostic tests, and to color pharmaceutical preparations.

Larrie Stone is a retired Dana College science professor.