Crown-glass is the hardest and most colourless kind of window-glass, made almost entirely of sand and alkali and a little lime, and used in connection with flint-glass for optical instruments in order to destroy the disagreeable effect of the aberration of colours. Research Crown-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be obtained from coal-tar products revolutionized dyeing as an industry, and the vegetable dye-stuffs were gradually superseded by the newer colours.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
Sepia is a dark-brown colouring matter secreted by the cuttle-fish, which uses it for defence, hiding behind it so as to escape predators. The sepia pigment is prepared by dissolving the dried contents of the cuttle-fish glands in dilute alkali and reprecipitating with an acid. Research Sepia
Cellulose is the cellular tissue of plants. It is a member of the carbohydrate family and is allied to starch. In plants, cellulose is normally combined with woody, fatty, or gummy substances. With some exceptions among insects, true cellulose is not found in animal tissues. Microorganisms in the digestive tracts of herbivorous animals break down the cellulose into products that can then be absorbed.
Cellulose is insoluble in all ordinary solvents and may be readily separated from the other constituents of plants. Depending on its concentration, sulphuric acid acts on cellulose to produce glucose, soluble starch, or amyloid; the last is a form of starch used for the coating of parchment paper. When cellulose is treated with an alkali and then exposed to the fumes of carbon disulphide, the solution yields films and threads. Rayon and cellophane are cellulose regenerated from such solutions.
Cellulose acetates are spun into fine filaments for the manufacture of some fabrics and are also used for photographic safety film, as a substitute for glass, for the manufacture of safety glass, and as a moulding material. Cellulose ethers are used in paper sizings, adhesives, soaps, and synthetic resins. With mixtures of nitric and sulphuric acids, cellulose forms a series of flammable and explosive compounds known as cellulose nitrates, or nitrocelluloses. Pyroxylin, also called collodion cotton, is a nitrate used in various lacquers and plastics; another, collodion, is used in medicine, photography, and the manufacture of artificial leather and some lacquers. A third nitrate, guncotton, is a high explosive. Research Cellulose
Ludwig Mond was a German chemist. He was born in 1838 at Cassel and died in 1909. Educated at Marburg and Heidelburg universities he went to England in 1862 to introduce a process for the recovery of sulphur from alkali waste and in 1873 partnered John Brunner to invent a process for creating soda - the Silvay or ammonia process - erecting a works near Norwich for the manufacture of soda. Research Ludwig Mond
Acidosis is a condition in which the body fluids tend to have a higher acid content than normal. The body has a variety of ways to compensate for mild acidosis, but prolonged acidosis can produce weakness, headache, and heavy or rapid breathing. Severe acidosis may lead to acidemia (a build-up of acids in the blood) which can result in coma and death. Acidosis itself is not a disease, but it may warn of the presence of a disease. It arises from disorders that cause the body to accumulate excess acid or to lose too much alkali. Most of these disorders are respiratory failures or metabolic failures. Respiratory acidosis results from such disturbances as severe lung disease, blockage of the upper air passages, and chest injury. Metabolic failures involve malfunctioning of the process by which the body changes food into energy and tissue. Metabolic acidosis arises from kidney failure, diabetes, poisoning, and severe diarrhoea. Treatment usually consists of correcting the underlying problem and administering sodium bicarbonate or another alkaline substance through a vein. Research Acidosis
Alkalosis is a condition in which a person's body fluids become too alkaline. The body adjusts to mild alkalosis but severe alkalosis can result in muscular weakness, convulsions, coma, and even death. Most cases of alkalosis arise from disorders or drugs that cause the body to lose too much acid, thus upsetting the normal balance of acid and alkali. Disorders that can result in alkalosis include prolonged vomiting and hyperventilation. Prolonged alkalosis causes excessive loss of hydrochloric acid from the stomach. During hyperventilation, a person exhales too much carbon dioxide, lowering the level of carbonic acid in the blood.
Alkalosis can arise from the prolonged use of such drugs as diuretics. Treatment of alkalosis usually consists of correcting the underlying disorder or reducing the drug intake. A solution containing a weak acid may be administered through a vein to help restore the body's normal acid- alkalibalance. Research Alkalosis
Alkali is a term first used to designate the soluble parts of the ashes of plants, especially of sea-weed. Now the term is applied to various classes of bodies having the following properties in common: (1) solubility in water; (2) the power of neutralizing acids, and forming salts with them; (3) the property of corroding animal and vegetable substances; (4) the property of altering the tint of many colouring matters thus, they turn litmus, reddened by an acid, into blue; turmeric, brown; and syrup of violets and infusion of red cabbages, green. The alkalis may be regarded as water in which part of the hydrogen is replaced by a metallic radicle. The caustic alkalis are strong alkalis which have a powerful corrosive action on the skin, and the common ones are potassium hydroxide or causticpotash, sodium hydroxide or causticsoda, and lithic hydroxide. A solution of ammonia in water is termed ammonia hydroxide or volatile alkali. It is a much feebler alkali than the others, and when the solution is heated all the ammonia is driven off. Other alkalis are calcium hydroxide or slaked lime, a solution of which in water is known as lime water; barium hydroxide and strontium hydroxide, derived from the metals barium and strontium. Research Alkali
The Probert Encyclopaedia was designed, edited and programed by
Matt and Leela Probert
Abbreviations
Research Crown-Glass
