Archil Purple


Archil may be regarded as the English, cudbear as the Scotch, and litmus

as the Dutch name for one and the same substance, extracted from

several species of lichens by various processes. These lichens, which

are principally collected on rocks adjacent to the sea, are cleaned and

ground into a pulp with water, treated from time to time with ammoniacal

liquor, and exposed with frequent agitation to the action of the

atmosphere. Peculiar principles existing in the lichens are, by the

joint instrumentality of the air, water, and ammonia, so changed as to

generate colouring matter, which, when perfect, is expressed. Soluble in

water and alcohol, this colouring principle yields by precipitation with

chloride of calcium a compound known as 'Solid French Purple', a pigment

more stable than the archil colours generally, but all too fugitive for

the palette.