This dye was well known in ancient times, and although descriptions are vague, it is usually thought that Roccella tinctoria was the main lichen used. The term was first used in England in the 14th century. In Europe various names have been used ...

Spain orciglia orciglio orchilla
Portugal urzella urzela 
Italy oricello 
Germany persio persis
England orchal orchil archil orchilla
France orseille orchal orsellé 

Here is a recipe for orchil: This description is by Roseto (1540) quoted by Hellot (1750) and from Kok.

"Take one pound of the Orselle of the Levant, very clean ; moisten it with a little urine add to this sal-ammoniac, sal-gemmae ("sel terrestre et fossile", des Bruslons, p. 184), and saltpetre, of each two ounces ; pound them well, mix them together, and let them remain so during twelve days, stirring them twice a day; and then to keep the herb constantly moist, add a little urine, and in this situation let it remain eight days longer, continuing to stir it; you afterwards add a pound and a half of pot-ash well pounded, and a pint and a half of stale urine. Let it remain still eight days longer, stirring it as usual after which you add the same quantity of urine, and at the expiration of five or six days, two drachms of arsenic ; it will then he fit for use".

The Early Chemistry

The first steps in understanding the origin of the purple colour were taken by Pierre Robiquet (born in Rennes 1780, died 1840) in1829 when he isolated orcine as large colourless prisms, from the lichen by extraction with ethanol. The purple dye obtained from orcine, now called orcinol, by reaction with ammonia and air he called orcéine.
Kane (1840) prepared coloured substances which he called azolitmin, spaniolitmin, erythrolein and erythrolitmin. 
Henry Edward Schunck (born in Manchester 16 August 1820, died at Kersal 13 January 1903) published several papers (1842-1847) about the isolation of  lecanoric acid  from the lichen.

For more recent chemistry, have a look at the orcein page.

This is a drawing of Roccella tinctoria
Roccella tinctoria
from Dillenius's Historia Muscorum (1742)


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