88. During a very long period, the inhabitants of Sweden, Scotland, Ireland, and sonic of the northern parts of England, have been in the practice of dyeing, by means of different species of lichen, macerated in urine. Of these, the Lichen onzlzhalides has been much used, under the name of cork, corker, and arcol; in Wales it is called kenkering. This lichen gives a dark crimson to wool and woollen stuffs. LinnRus says, that it is pro duced in great abundance in the island of Aland, in the Baltic. The Lichen tartareus, which grows on limestone rocks, yields a similar colour, and has been long used as a dye by the peasants of Wales and the Orkneys. The inhabitants of West Gothland prepare a beautiful crim son dye from this lichen, which, under the name of Byttelet, is used over all Sweden. It also forms an ar ticle of exportation, and is known in this country by the name of Cudbear, a name given to it by the late Dr Cuth bert Gordon, who obtained a patent for its preparation. proper season, and in places where the Lichen Tartareus is produced, one person may collect from twenty to thirty pounds of it daily. It should be allowed five years growth before it is gathered ; and it is prepared for use by washing and drying it, which commonly re duces it to half the original weight. It is macerated and stirred in wooden troughs, in the same manner as the perelle at Clermont ; only aqua ammonia prepared from human urine is employed, instead of urine itself. Dr Bancroft, who has frequently prepared the colouring matter yielded by this lichen, states that the ammonia has important advantages over the urine; and that he is convinced that the 'alum recommended by Cocci is com pletely useless, while the arsenic is not only useless, but dangerous. He also thinks that much labour in stirring, and much waste of volatile alkali, might be avoided, by employing hogsheads instead of fixed troughs. For this purpose, he recommends the lichen to be first ground in a mill, and afterwards to be introduced into the hogshead along with a suitable quantity of liquid ammo nia. The bung-hole being well secured, the hogshead might be rolled from time to time, or subjected to any other kind of agitation.
89. The colours obtained from cudbear prepared by these processes, possess great beauty and lustre at first, but they quickly fade, and ought never to be employed, unless for the purpose of heightening the brilliancy of some more permanent dye. The colour extracted from the rocella, or orchella, is more beautiful and less fugi tive than that yielded by any other species of lichen; but none of these colours are lasting. Cudbear is chiefly employed in this country to give body and lustre to the blues dyed with indigo ; it is also sometimes used as a ground for madder reds. It stains marble of a durable violet colour. Dufay says, that lie has seen marble stained with this colour unaltered at the end of two years.
90. The infusion of archil is of a crimson, inclining to violet. Acids impart to it a red colour : but as it con tains ammonia, by which its natural colour has been al ready modified, fixed alkalies produce little change on it, only rendering its colour somewhat deeper, and more inclined to violet. Alum forms with it a dark red preci pitate, without rendering the colour more permanent. The nitro-muriate of tin makes the colour died with it to approach nearer to a crimson, which is less fugitive than when that ingredient is not employed.
91. Besides the lichens, whose. colouring matter is prepared with ammonia, some of them afford substan tive dyes less beautiful, but more permanent, by mere boiling with water. Of these, the muscus pulmonarius of Casp5.r Bauhine, or the lichenoides pulmonium reti culatum vulgare marginibus peltiferis of Dillenius, known in the northern parts of England by the name of rags, or stone-rag dyes, without an mordant, a very durable dark-brown colour upon white wool or cloth; and a fine lasting black upon wool or cloth which has previously received a dark blue from indigo. See Ban croft, Perm. Col. i. 305.
III. Of Mineral Substantive Colours.
92. The greater number of mineral substances used in dyeing, are employed chiefly with a view of attaching colouring matters to stuffs, or of heightening their lus tre after they have been so applied. Some of them, however, particularly iron and copper, are occasionally employed for giving substantive colours.
93. Iron, in every form of its solution, has a strong affinity for linen and cotton, and readily combines, in the state of an oxide, with their fibres. The colours which it affords vary with the degree of oxidation; but as the oxide, in all its combinations, is disposed to attract more oxygen from the atmosphere, these colours all terminate in the rusty colour commonly called iron-mould. This absorption of oxygen, being a kind of slow combustion, renders the oxide corrosive, and gradually injures the texture of the cloth. The rigidity which it occasions in the fibres, also renders them more brittle, and less du rable. Hence iron-moulds at last produce holes. This injurious property of the oxide of iron, is in some de grec counteracted by combining the oxide with other substances; but there is reason to fear, that, in every lidition, the oxide of iron is hurtful to stuffs. It is to property that the rottenness SO generally complained of, with respect to the black dye, is to he ascribed.
9.1. The oxide of iron is usually applied to linen or cotton in combination with some acid. Vinegar was usually tmployed for this purpose ; and the resulting salt, the acetate of iron, has been long known to dyers under the name of iron liquor. Another acid has of late bean frequently substituted for the vinegar, called the py oligneous. w inch is distilled from wood, and is in reality the acetic acid in combination with a portion of clop) reumatic oil. This compound acid dissolves iron than the acetic, and forms a salt which is more use ful in dyeing than the acetate. The oxide combines with the acid at different stages of oxidation; but the resulting solution forms the most intimate and permanent union with the fibres of linen and cotton, when the oxi dation is greatest. M. Cnaptal has ascertained that the different buff colours, and the imitations of nankeen, may be greatly improved by combining the oxide of iron with alumine. Ile accordingly first impregnates the linen or cotton with a solution of the oxide of iron in the pyroligneous, or some other vegetable acid, marking three degrees on the areumeter of Beaun.e. and, alter wringing it propel ly, plunges it inuneuiately into a so lution of potash marking two degrees, with which a sa turated solution of alinu htis been mixed, but so as not to precipitate the aluminc. By this mixture, the colour of the oxide is heightened, and the cloth acquires an agreeable, smooth, and soft appearance.—Sce Ann. de Chia. xxvi. p. 270.