Azuline is a coal-tar blue dye that became popular for colouring silk in 1861. It was one of the first synthetic dyes. [1] The name was a combination of " azure" and " aniline". A variant of the name was "Azurine". The word was introduced as a colour term about the same time as "mauve" and "magenta", but it has not survived in the English language. [2]
The dye is made from phenol, first oxidising it with oxalic acid and sulfuric acid to make a red substance called rosolic acid. By treating this with ammonia, a dye called red coralline or péonine was made. When reacted with aniline, the blue azuline was produced. This was invented by Jules Persoz in Paris. A company in Lyon called Guinon, Marnas & Bonnet bought the process and established a patent. [3] In 1862 azuline was selling for 450 francs per kilogram. [4]
Chemists at first did not know the structure of the molecules in the coal tar dyes including azuline. [5]
Use of azuline was superseded by aniline blue. [6]
As a solid, azuline has a metallic appearance with a copper red colour. It hardly dissolves in water, but does dissolve in alcohol. In alcohol it has a strong blue colour, but still has a red tinge. [7] The dye is colourfast, resisting fading by light. [5] Sulfuric acid solution gives a red solution. Iodine destroys the substance. Ammonium sulfide reduces the colour to pale yellowish-brown. [8]
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: CS1 maint: unfit URL (
link) Originally in American Dyestuff Reporter vol 81 no 11