DIRECT CoLouxs.—The characteristic feature of the dyestuffs belonging to this class is that they dye
See also:cotton " direct "—i.e. without the aid of mordants . Two distinct series of colouring matters of this
See also:group may be distinguished—namely, Direct Cotton
See also:Colours and Sulphide Colours . (a) Direct Cotton Colours.—The colours of this class are frequently called the Substantive Cotton Colours, Benzo Colours, Diamine Colours,
See also:Congo Colours . Considered from the chemical point of view, they are mostly
See also:alkali salts of sulphonated tetrazo colours obtained by diazotizing certain diamido .compounds, e.g. benzidine, diamido-stilbene, &c., and uniting the products thus obtained with various
See also:amines or phenols . The first colouring
See also:matter of this class was the so-called Congo red, discovered in 1884, and since that
See also:time a very
See also:great number have been introduced which yield almost every variety of
See also:colour . The method of dyeing cotton consists in merely boiling the material in a solution of the dyestuff, when the cotton absorbs and retains the colouring matter by reason of a
See also:special natural
See also:affinity . The concentration of the dyebath is of the greatest importance, since the amount of colour taken up by the fibre is in an inverse ratio to the amount of dye liquor
See also:present in the bath . The addition of I to 3 oz. sodium sulphate and to oz. carbonate of soda per
See also:gallon gives deeper colours, since it diminishes the solubility of the colouring matter in the
See also:water and increases the affinity of the cotton for the colouring matter . An excess of sodium sulphate is to be avoided, otherwise precipitation of the colouring matter and imperfect dyeing result . With many dyestuffs it is preferable to use a to s oz.
See also:soap instead of soda . On cotton the dyed colours are usually not very fast to
See also:light, and some are sensitive to alkali or to acid, but their most serious defect is that they are not fast to washing, the colour tending to run and stain neighbouring
See also:fibres . Their fastness to light and washing is, however, greatly improved by a
See also:short (2
See also:hour) after-treatment with a boiling solution of copper sulphate (3 %), with or without the addition of bichromate of potash (I %) .
See also:silk are dyed with the direct colours either neutral or with the addition of a little acetic acid to the dyebath . On these fibres the dyed colours are usually faster than on cotton to washing, milling and light; some are very fast even to light—e.g . Diamine fast red, chrysophenine,
See also:Hessian yellow, &c . Many of the Direct Colours are very useful for dyeing plain shades on union fabrics composed of wool and cotton, silk and cotton, or wool and silk . Owing to the facility of their application, they are also very suitable for use as
See also:household dyes, especially for cotton goods . A few
See also:vegetable dyestuffs belong to this class, notably
See also:saffron, annatto and safflower, but they all yield colours which are fugitive to light, and they are now of little importance . Turmeric is the underground
See also:stem or tuber of Curcuma tinctoria, a plant growing abundantly in the East Indies . It dyes cotton, wool and silk in a bath acidified with acetic acid or
See also:alum, yielding a bright yellow colour which is turned
See also:brown by alkalis . Saffron consists of the stigmata of the flower of
See also:Crocus sativus, which is grown in
See also:Austria, France and Spain . It dyes a bright orange-yellow colour . Annatto is the pulpy mass surrounding the seeds of Bixa orellana, a plant which grows in South America—e.g . Brazil,
See also:Cayenne, &c .
It dyes cotton and silk in an alkaline or soap bath an orange colour, which is turned red by acids . Safflower consists of the dried florets of Carthamus tinctorius, which is grown in the East Indies,
See also:Egypt and
See also:Europe . Cotton is dyed a brilliant
See also:pink colour by working it in a
See also:cold alkaline (sodium carbonate) extract of the colouring matter, while gradually acidifying the solution with citric acid (lime-juice) . The Direct Colours which are derived from
See also:tar products are very numerous indeed; they are largely employed, and occupy a very important position among dyestuffs, The following
See also:list includes the
See also:principal coal-tar colours of this group: Red.—Congo red, brilliant Congo, benzopurpurine, brilliant purpurine, deltapurpurine, diamine
See also:scarlet, diamine fait red, rosazurine, salmon red, erica, Titan pink, St Denis red,
See also:Columbia red, naphthylene red, Congo rubine, acetopurpurine, dianol red, thiamine
See also:crimson, geranine, brilliant geranine, Columbia fast scarlet, benzo fast scarlet, thiamine red, diamine
See also:Dongola red, rosophenine . Orange.—Congo orange, benzo orange, toluylene orange, mikado orange, brilliant orange, Columbia orange, diamine orange, pyramine orange, benzo fast orange . Yellow.—Chrysamine, cresotin yellow, diamine yellow,
See also:carbazol yellow, chrysophenine, Hessian yellow, curcumine yellow, thiazol yellow, thioflavine S, oriol,
See also:mimosa yellow, Columbia yellow, cotton yellow, chloramine yellow, direct yellow, diamine fast yellow, diamine gold,
See also:sun yellow, stilbene yellow, chlorophenine, oxyphenine .
See also:olive, Columbia green, benzo green, diamine green, direct green,
See also:diphenyl green, oxamine green,
See also:eboli green . Blue.—Azo blue, benzoazurine, brilliant azurine, sulphon-azurine, diamine blue, benzo
See also:indigo blue, benzo black blue, Chicago blue, Columbia blue,
See also:Erie blue,
See also:Zambezi blue, benzo cyanine, Congo blue, diamine
See also:sky blue, brilliant benzo blue, benzo chrome black blue, oxamine blue, diphenyl blue, diamineral blue, diaminogene, benzo fast blue, diazo indigo blue, brilliant chlorazol blue .
See also:purple, Congo Corinth, heliotrope, Congo violet, diamine violet, Hessian violet,
See also:azo violet, benzo violet, violet black, diamine
See also:Bordeaux, chlorantine
See also:lilac, diphenyl violet, triazol violet, Columbia violet . Brown.—Benzo brown, Congo brown, toluylene brown, diamine brown, cotton brown, Hessian brown, terra-cotta, mikado brown,
See also:catechu brown, wool brown, Columbia brown, Zambezi brown, benzo chrome brown, direct fast brown, direct
See also:bronze brown, chloramine brown, triazol brown, toluylene brown, dianol brown, Crumpsall direct fast brown . Black.—Diamine black, Columbia black, Nyanza black, Tabora black, Zambezi black, chromanil black, benzo black, benzo fastblack, direct blue black,
See also:Pluto black, oxydiamine black, diamine
See also:jet black, polyphenyl black, union black, triazol black, Titan black, cotton black, oxamine black .
See also:Grey.—Benzo grey, benzo black, azo
See also:mauve, diaminogene, neutral grey .
(b) Sulphide Colours.—These dyestuffs are only suitable for dyeing the vegetable fibres, since they must be applied in a strongly alkaline bath . The dyestuff Cachou deLaval, discovered in 1873, was the first member of this group, and was obtained by melting a mixture of sodium sulphide and various organic substances—e.g.
See also:bran, saw-dust, &c . In
See also:recent years numerous other dyestuffs have been added to the list, namely, grey, blue, green, brown, and especially black colours, by submitting certain definite amido compounds of the aromatic series to a similar treatment with sodium sulphide or sodium thiosulphate, and subsequent oxidation . The mode of dyeing with these colours is based on the fact that they are soluble in an alkaline reducing
See also:agent, and if the cotton is worked in the solution, subsequent oxidation develops the colour, which is fixed upon the fibre in an insoluble
See also:condition . The material is boiled for about one hour in a solution of the colour (to to 15 %), with the addition of sodium carbonate (I to to %),
See also:salt (To to 20%), and sodium sulphide (5 to 30 %) ; it is then washed in water, and may be
See also:developed by
See also:heating in a bath containing 2 to 5 % of bichromate of soda, and 3 to 6 % acetic acid . A final washing with water containing a little soda to remove acidity is advisable . The sulphide colours are remarkable for their fastness to light, alkalis, acids and washing, but unless proper care is exercised the cotton is
See also:apt to be tendered on being stored for some time . The following list includes some of the most important of the colours of this class: Yellow.—Immedial yellow, pyrogene yellow,
See also:sulphur yellow, thion yellow, thiogene yellow . Orange.—Eclipse phosphine, immedial orange, pyrogene orange, thion orange, thiogene orange . Green.—Pyrogene green,
See also:Italian green, eclipse green, pyrol green, immedial green, katigene green, thionol green . Blue.—Immedial blue, immedial sky blue, eclipse blue, katigene indigo, pyrogene blue, sulphur blue, thion blue, thiogene blue . Violet.—Katigene violet, thiogene heliotrope, thiogene purple .
Brown.—Pyrogene brown, pyrogene yellow, Cachou de Laval, thiocatechine, katigene black brown, eclipse brown, immedial. brown, katigene brown, dianol brown . Grey and Black.—Pyrogene grey, Vidal black, immedial black, katigene black,
See also:anthraquinone black, St Denis black, amidazol black,
See also:cross dye black, eclipse black,
See also:carbide black, thiogene black, sulphaniline black, sulfogene black, pyrogene black, dianol black, sulphur black, thion black, kryogene black . This class of colours is continually increasing in number, and for certain purposes in cotton dyeing the group has acquired great importance .
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