Crystal dyeing history

Humans have used dyes to create color since the dawn of history. Until the mid-nineteenth century, all dyes were of natural origin. Many came from plants, such as indigo, a dark blue dye that was extracted from the leaves of a native East Indian plant. In 1856, the young English chemist William Perkin stumbled upon the first synthetic dye. Perkin was trying to synthesize quinine, a valuable antimalaria dmg. None of his experiments met with success. As he was about to discard the residue from yet another failed reaction, Perkin noticed that it was colored with a purple tinge. He washed the residue with hot alcohol and obtained a purple solution from which strikingly beautiful purple crystals precipitated. Perkin had no idea what the substance was or what reactions had created it, but he immediately saw its potential as a new dye. 

As early as 1969, Pedersen was intrigued by the intense blue colour observed upon dissolution of small quantities of sodium or potassium metal in coordinating organic solvents in the presence of crown ethers. Indeed, the history of alkali metal (as opposed to metal cation) solution chemistry may be traced back to an 1808 entry in the notebook of Sir Humphry Davy, concerning the blue or bronze colour of potassium-liquid ammonia solutions. This blue colour is attributed to the presence of a solvated form of free electrons. It is also observed upon dissolution of sodium metal in liquid ammonia, and is a useful reagent for dissolving metal reductions , such as the selective reduction of arenes to 1,4-dienes (Birch reduction). Alkali metal solutions in the presence of crown ethers and cryptands in etheric solvents are now used extensively in this context. The full characterisation of these intriguing materials had to wait until 1983, however, when the first X-ray crystal structure of an electride salt (a cation with an electron as the counter anion) was obtained by James L. Dye and... 

Dyes have a long history of use in medicine both for diagnostic and therapeutic purposes. Thus, crystal violet (76) is used for staining bacteria (Gram test), and the azo dye Prontosil rubrum (77) was the first drug that produced the active agent sulfanilamide (78) on reduction in the body [67],... 

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