Archil or orchil is a red, violet, or purple colouring matter obtained from various kinds of lichens, the most important of which are the Roccella tinctoria and the Roccella fuciformis, natives of the rocks of the Canary and Cape Verde islands, Mozambique and Zanzibar, South America, etc, and popularly called dyer's-moss. The dye was used for improving the tints of other dyes, as from its want of permanence it could not be employed alone. The aniline colours largely superseded it. Cudbear and litmus are of similar origin. Research Archil
Blue is one of the seven colours into which the rays of light divide themselves when refracted through a glassprism, seen in nature in the clear expanse of the heavens; the term is also applied to a dye or pigment of this hue.
The substances used as blue pigments are of very different natures, and derived from various sources; they are all compound bodies, some being natural and others artificial. They are derived almost entirely from the vegetable and mineral kingdoms. The principal blues used in painting are ultramarine, which was originally prepared from lapis-lazuli or azure-stone - a mineral found in China and other oriental countries - but, as now prepared, it is an artificial compound of china-clay, carbonate of soda, sulphur, and charcoal; Prussian or Berlin blue, which is a compound of cyanogen and iron; blue bice, prepared from carbonate of copper; indigo blue, from the indigo plant. Besides these, there are numerous other blues used in art, as blue-verditer, smalt- and cobalt-blue, from cobalt, lacmus or litmus, etc.
Before the discovery of aniline or coal-tar colours dyers chiefly depended for their blues on woad, archil, indigo, and Prussian blue, but now a series of brilliant blues are obtained from coal-tar, possessing great tinctorial power and various degrees of durability.
Blue as a colour ranges from green-blue (turquoise) through to purple-blue (indigo).
Alice blue - A very light greenish-blue colour.
Aquamarine - A bluish-green colour.
Azure - A deep blue colour reminiscent of the sky.
Aquamarine - A pale greenish-blue colour.
Bice blue - A medium blue colour
Cambridge blue - A light blue colour.
Cobalt blue - A deep blue colour with a greenish-tint. The colour of old blue glass.
Dyeing is the art of giving colour to textile and other articles in such a way that the colours are more or less permanent, and not readily affected by the action of light, washing, etc. Like spinning and weaving it was originally a home industry, as it still is in many places. Until about 1850 natural dye-stuffs alone were employed, but the discovery of dyes of all colours that can be obtained from coal-tar products revolutionized dyeing as an industry, and the vegetable dye-stuffs were gradually superseded by the newer colours.
Before dyeing, the materials have generally to be cleansed or bleached to get rid of undesirable colouring matters or impurities; and frequently a textile material is subjected to some subsidiary treatment in order to obtain special effects. For example, cottonyarn may be subjected to the action of strong causticsoda ('mercerizing' process) while in a state of great tension, in order to give it a permanent silky lustre.
Dyeing is not only an art, it is also a branch of applied chemistry. One fundamental principle is, that the colouring matter and other necessary substances must be applied in a state of solution, and while in direct contact with the fibre they must be rendered insoluble, so that they are precipitated within or upon the fibre and thus permanently fixed. The method of effecting this varies greatly according to the fibre and the colouring matter employed. As a rule the vegetable and the animal fibres are dyed by very different methods. The affinity of the animal fibres for certain colouring matters is often so great that they are readily dyed by simple immersion in hot colour solutions;
but this simple process is not generally sufficient. According to the method of their application in dyeing the following groups: of dye-stuffs may be distinguished: Avid Colours, Basic Colours, Direct Colours, Developed Colours, Mordant Colours, Miscellaneous Colours, Reactive Colours.
The acid colours are so called because they are of an acid character and are applied in an acid dye-bath. As a rule, they are only suitable for dyeing the animal fibres, e.g. wool and silk, also leather, horn, feathers, etc. Only a few vegetable dye-stuffs belong to this class, for example, the purple colour orchil and the blue colour indigo extract. On the other hand, the acid colours derived from coal-tar - and increasingly petroleum - are very numerous and yield a great variety of hues - red, orange, yellow, green, blue, violet, brown, and black, each with its particular name.
The basic colours are so called because their essential constituents, to which they owe their dyeing power, are organicbases. The bases themselves are colourless and too insoluble in water to be of use, hence they are employed in the form of their soluble coloured salts, usually the hydrochlorides of the colour-bases. Their solutions are precipitated by tannic acid, because it combines with the colour-bases to form insoluble tannates. Wool, silk, and animal substances generally have a direct attraction for colour-bases, and hence these fibres are readily dyed by simple immersion in hot aqueous solutions of the basic colours. Cotton and linen, on the other hand, are not dyed so readily; they need first to be prepared or impregnated with tannic acid, and thus prepared are said to be mordanted, the tannic acid in this connection being styled the mordant. Most of the colours of this class are fugitive to light, and all but one, barberryroot, are derived from coal-tar products.
The direct colours are so called because they dyecotton direct, that is, without the aid of any mordanting process. The first of this class derived from coal-tar was congo red, discovered in 1884; this group includes a very great variety of fast colours, and forms, indeed, one of the most important and valuable series of dye-stuffs employed. Cotton, linen, and the vegetable fibres generally are dyed in the simplest possible manner by merely boiling them in a solution of the dye-stuff, with or without the addition of a little soap, carbonate or sulphate of soda, etc. Wool and silk are frequently dyed in the same manner as cotton. Very few vegetable dye-stuffs belong to the direct colours, e.g. Safflower, Turmeric, Saffron, Annatto. They are all fugitive, and have been of little or no importance to the dyer since the end of the 19th century. The coal-tar colours of this class, on the other hand, are extremely numerous.
The developed colours include a variety of colours which are formed in situ upon the fibre by the successive application of two or more substances. These colours are all of coal-tar origin. A number of them belong to the so-called azo colours, derived from compounds containing nitrogen.
The mordant colours form one of the most important classes of colouring matters, for they include not only most of the vegetable dye-stuffs, e.g. madder, logwood, fustic, etc, but also many valuable fast coal-tar colours, commonly known as the alizarin colours, after their typical representative, alizarin. These mordant colours have by themselves very little colouring power, as a rule, and if employed alone in dyeing give little or no result. If applied, however, in conjunction with metallic salts, notably those of chromium, aluminium, iron, tin, and copper, they each yield a variety of colours, according to the metallic salt employed. In employing them usually two distinct operations are involved: first, that of applying the metallic salt or mordant, called the mordanting process ; and second, that of dyeing proper, in which the mordanted material is boiled in a solution or decoction of the dye-stuff. During the dyeing operation the colouring principle of the dye-stuff combines with the metallic salt already upon the material, and the colour is thus produced and fixed upon the fibre. The method of mordanting varies with the fibre and the metallic salt employed. The vegetable dye-stuffs of this class include Madder, Sapanwood, Camwood, Barwood, Old Fustic, Young Fustic, Quercitron Bark, Persian Berries, Weld, Logwood. Madder was formerly the most important and highly valued of the dye-stuffs of this class, being especially employed to produce the fine 'Turkey-red' dye; but was entirely superseded by the coal-tar colour alizarin towards the end of the 19th century.
Reactive colours combine directly with the fibre being dyed through a chemical reaction and result in a fast colour. The first ranges of reactive dyes for cellulose fibres were introduced in the mid-1950s.
Similarly, the employment of cochineal (an insect dye) has also greatly diminished through the introduction of the cheaper colours. Camwood and barwood are almost entirely used in wool-dyeing, either in conjunction with the indigo-vat or for the purpose of dyeing various shades of brown. Old fustic is the most important of the yellow mordant dye-stuffs, and the colours are fast although not very brilliant. Young fustic yields fugitive colours, and has been little used since 1900. Quercitron bark is an excellent dye-stuff employed by wool-dyers for the production of bright orange and yellow colours. Persian berries and weld, a species of wild mignonette, are both excellent dye-stuffs, but their employment is now limited. Logwood is largely employed by wool, silk, and cotton dyers for dyeing black and dark-blues, which, although fast to washing, are only moderately so towards light. During the 20th century dyewoods were gradually replaced by coal-tar colours.
Among miscellaneous colours are several dye-stuffs applied in a distinct manner. Indigo is a dark-blue powder quite insoluble in water, but can be rendered soluble for dyeing purposes by two methods. The first method converts the indigo into so-called indigo extract, which is sold as a blue paste and applied as an acid colour in dyeing wool and silk. In the second method the indigo-blue is converted into indigo-white, which readily dissolves in the alkalipresent, the solution thus obtained being called an indigo-vat. If cotton, wool, or silk is steeped for some time in the clear yellow solution of such a vat, and then exposed to the oxidizing influence of the air, they are dyed a permanent blue. The indigo-white absorbed by the fibre loses its acquired hydrogen, and thus insoluble indigo-blue is regenerated within and upon the fibre. Aniline black is a valuable colour, produced direct upon the fibre by the oxidation of aniline, and remarkable for its extreme permanency.
Catechu is a vegetable dye-stuff used in dyeing cotton and woollen brown. On wool, catechu yields khaki browns in single bath by using copper sulphate as the mordant. On silk it is largely employed for weighting purposes in the process of dyeing black. Chrome Yellow, Iron Buff, Prussian Blue, and Manganese Brown, employed in cotton dyeing, are frequently classed as mineral colours. Chrome yellow is obtained by immersing cotton successively in solutions of acetate of lead and bichromate of potash, whereby the yellow precipitate of chromate of lead is fixed upon the fibre. Iron buff is obtained in a similar manner by the successive application of iron sulphate and carbonate of soda, and finally developing the full colour by washing with water and exposure to air. The buff colour is really due to the precipitation of oxide of iron on the cotton. Prussian blue is at once developed by passing the buff-dyed cotton through an acidified solution of potassium ferrocyanide. The production of manganese brown on cotton is similar to that of iron buff. The brown colour ultimately produced upon the fibre is an oxide of manganese. The mineral colours are very useful for certain purposes, and are to be regarded as very fast to light. Research Dyeing
Anilisim or aniline poisoning, is a name given to the aggregate of symptoms which often showed themselves in those employed in aniline works at the end of the 19th century and start of the 20th century, resulting from the inhalation of aniline vapours. It may be either acute or chronic. In a slight attack of the former kind, the lips, cheeks, and ears become of a bluish colour, and the person's walk may be unsteady; in severe cases there is loss of consciousness. Chronic anilism is accompanied by derangement of the digestive organs and of the nervous system, headaches, eruptions on the skin, muscular weakness, etc. Research Anilism
Acetaldehyde is a colourless liquid with a pungent, fruity odour. It is used primarily as a chemical intermediate, principally for the production of acetic acid, pyridine and pyridinebases, peracetic acid, pentaerythritol, butylene glycol, and chloral. It is used in the production of esters, particularly ethyl acetate and isobutyl acetate. It is also used in the synthesis of crotonaldehyde, flavour and fragrance acetals, acetaldehyde 1,1-dimethylhydrazone, acetaldehyde cyanohydrin, acetaldehyde oxime, and various acetic esters, paraldehyde, metaldehyde, polymers, and various halogenated derivatives. Acetaldehyde is used in denatured alcohol. In the past it was a chemical intermediate for 2-ethyl-1-butanol, glyoxal, acrolein, and acetaldehyde-aniline condensate. Acetaldehyde has been used in the manufacture of aniline dyes and synthetic rubber, to silvermirrors, and to hardengelatine fibres.
Acetaldehyde has been used in the production of polyvinyl acetal resins, in fuel compositions, and to inhibit mould growth on leather. It is also used in the manufacture of disinfectants, drugs, perfumes, explosives, lacquers, varnishes, photographic chemicals, phenolic and urea resins, rubber accelerators, antioxidants, and room air deodorisers. It is also a pesticide intermediate.
Acetaldehyde is a compound for the intended use as a flavouring agent and adjuvant. It is an important component of food flavourings added to milk products, baked goods, fruit juices, candy, desserts, and soft drinks; the concentration of acetaldehyde in food is usually up to .047%. It is an especially useful synthetic flavouring ingredient to impart orange, apple, and butter flavours, and is used in the manufacture of vinegar and yeast and as a fruit and fish preservative.
Acetaldehyde is a volatile and flammable liquid. It is miscible in water, alcohol, ether, benzene, gasoline, solvent, naphtha, toluene, xylene, turpentine, acetone, and other common organic solvents. It is a highly reactive compound that undergoes numerous condensation, addition, and polymerisation reactions. It is dangerous when exposed to heat or flame; it can react vigorously with oxidising material, acid anhydrides, alcohols, ketones, phenols, halogens, isocyanates, and strong alkalis and amines. It is also incompatible with acids, bases, alcohol, ammonia, amines, phenols, ketones, and hydrogen cyanide. It will polymerise readily in the presence of trace metals. Acetaldehyde can form unstable or explosive peroxides with exposure to the air. It may polymerise under the influence of air and heat, acids, or bases with potential of fire or explosion. It is polymerised violently by concentrated sulphuric acid. Rubber products decompose on contact with acetaldehyde, but it is not corrosive to most metals. It is also known as acetic aldehyde, ethanal, NCI-C56326, and ethyl aldehyde. Research Acetaldehyde
Aniline (Phenylamine or amido-benzene) is an oily liquid occurring in coal-tar and made by the reduction of nitro-benzene and used in the manufacture of chemicals, dyes and drugs. It was discovered in 1826 by Unverdorben among the products of distillation of indigo. In 1856 Bechamp obtained it from nitro-benzene. Benzene, when acted on by nitric acid, produces nitro-benzene; and this, when reduced with iron-filings or scraps, and a small amount of hydrochloric acid, yields aniline. It is also prepared by passing an electric current through a mixture of nitro-benzene and sulphuric acid. It is a colourless oily liquid, somewhat heavier than water, with a peculiar smell, and a burning taste. It is a basic substance, and, like the alkaloids, forms salts with different acids. An important group of aniline dyes are the azo dyes, obtained by the action of nitrous acid and the phenols on aniline. The manufacture of these aniline dyes was introduced in 1856 by Mr. Perkin of London but were most largely manufactured in Germany. Research Aniline
Benzene, benzine or benzol is a a liquid hydrocarbon obtained from coal-tar or distillate of petroleum obtained from benzol by treating it with sulphuric acid and then distilling, used as a solvent in dry cleaning and painting. Benzene was discovered by Faraday in the oils of portable gas in 1825 and obtained by Mitscherlich from benzoic acid in 1834, and by Mansfield from coal tar in 1848 (he also died as the result of burns sustained while experimenting with benzene). It has the formulae CgHg and is quite colourless, of a peculiar agreeable odour and is used by manufacturers of india-rubber and gutta-percha, on account of its great solvent powers, in the preparation of varnishes, also for removing grease from fabrics, gloves, etc. It is the parent substance for most of the aniline dyes and for other substances, e.g. saccharin. It is inflammable, burning with a very smoky flame. Research Benzene
Coal-tar or gas-tar is a thick black viscous liquid produced by the destructive distillation of coal for the manufacture of illuminating gas, consisting principally of oily hydrocarbons. It passes over with the gas into the condensers along with ammonia liquor, but being heavier than the latter, it is easily separated from it when the whole is allowed to stand. It was formerly of comparatively little use; but ince the 19th century a great number of valuable products have been derived from it by distillation, such as ammonia, naphtha, creasote, carbolic acid, and benzene, while it is also the source of the whole series of aniline colours, and other dyes, of alizarine, salicylic acid, etc. Research Coal-tar
Abbreviations
Research Archil
