A Manual for Students of Chemistry and Dyeing
By
M. Fort, M.Sc. (Leeds) Late Lecturer in Dyeing in the Bradford Technical College and L. L. Lloyd, Ph.D. (Bern) Lecturer in Organic and Technical Chemistry in the Bradford Technical College
Cambridge: at the University Press 1919
(First edition 1917, reprinted 1919)These dyestuffs differ from each other very little in general properties. The commercial products are mainly basic dyestuffs.
They all give leuco compounds on reduction, which reoxidise in presence of air. Hence the volumetric estimation with titanous chloride is done in a CO2 atmosphere. They have the following characteristic groupings: [-]
Azine Dyestitffs. - Azonium bases are derived from azines by linking an organic radicle to one of the nitrogen atoms, which is thereby changed from trivalent to pentavalent nitrogen. These bases are themselves dyestuffs, but are too feeble for commercial use without the introduction of auxochrome groups. A new branch of azines in the anthraquinone series possesses valuable vat-dyeing properties and other distinctive features which require separate treatment (see Anthracene Derivatives). The introduction of auxochrome groups into azines and azonium bases has furnished a large number of commercial dyestuffs. The first dyes of this class, safranines and indulines, were obtained by purely empirical methods. Their production by methods of oxidation involved the intermediate formation of indamines. Thus, when an ortho-amido indamine is heated in aqueous solution, it is transformed to an azine, i.e., changes from blue to red, the leuco compound formed intermediately, oxidising in the presence of air.
[-]
The simplest azine type, diphenazine, obtained by heating pyrocatechol and o-phenylene diamine, may be written [-]
Azines appear to be tautomeric bodies possessing the symmetrical type of constitution in the almost colourless free state. The ortho-quinonoid constitution (quinoxaline) is ascribed to the intensely coloured salts of azine bases, e.g., [-]
In many azine dyestuffs the presence of auxochrome groups permits of a p-quinonoid structure being assigned, as well as the ortho type shown above, e.g., Neutral Red.
These dyestuffs are, however, generally written with an ortho-quinonoid constitution [-]
Then, again, an alternative is offered, i.e., to which nucleus the quinone bonds should be attached. It is often difficult to decide among the existing possibilities in assigning quinonoid formulae to azine dyestuffs, while the symmetrical formula usually can be safely assigned, for the time being at any rate.
The azine class can be subdivided into certain well marked groups, typical members of which will suffice.
The quinoxaline class only contains one member. The parent substance is quinoxaline or phenazine.
[-]
When phenanthraquinone is condensed with o-amido diphenylamine in glacial acetic acid solution, a basic orange yellow dye is obtained, Flavinduline O, II (B.).
[-]
The mono and diamidodiphenazines are called eurhodines, e.g., Neutral Red is of the eurhodine class.
The mono and di-oxy derivatives corresponding to eurhodines are called eurhodols.
The azonium class derived from phenylphenazonium chloride includes the aposafranines and aposafranols, [-] which are respectively mono-amido derivatives of phenylphenazonium chloride and monoxy derivatives. (The auxochrome groups are meta to the pentavaleut N atom.)
The safranines are diamido-phenylphenazonium compounds. In a typical safranine both auxochrome groups are in the m-positioir to the pentavalent N atom. The corresponding di-oxy derivatives are called safranols. Bodies of the safranine type, however, having the amido groups phenylated, are called mauveines, while the introduction of other phenyl-amido groups into mauveines gives indulines.
The aposafranines derived from naphthophenazine have also been given special names according to the position of the amido group. When this is in the naphthalene ring they are called rosindulines, e.g., Induline Scarlet (B.) is a typical rosinduline.
[-]
With the amido group in the phenyl nucleus the isorosindulines are obtained, e.g., Neutral Blue (C.).
[-]
These dyes are all basic dyes and find their chief use on cotton, being applied on a tannin mordant.
Induline Scarlet also finds use as a catalyst along with formaldehyde-hydrosulphite reducing agents. By its use it is possible to discharge Naphthylamine Bordeaux in calico printing, which is unsatisfactorily performed by use of fonnaldehyde-hydrosulphites alone. Rongalite Special (B.), and certain other "special" commercial brands of these reducing agents, contain the above dyestuff as catalyst.
The Nigrosines are grey and black dyestuffs, ot which little is known as to constitution, except tkit they are related to the indulines.
Eurhodines. - This small and unimportant class may be shortly dealt with. The method of obtaining Neutral Red above described is typical. Any of the alternative methods of synthesis available for the required indamine may be employed.
Further condensation proceeds readily on heating in aqueous solution as in the case of Neutral Red.
The eurhodines are weak bases forming red monoacid salts and green di-acid salts. Only the former come into consideration for dyestuffs as the latter are dissociated in aqueous solution.
The eurhodols obtained by replacement of amido groups by oxy groups in eurhodines have no commercial importance.
Safranines. - The elucidation of the constitution of these dyestuffs presented great difficulty, and is mainly due to Hofinann, Witt, Nietzki and Bernthsen. The following facts are to be considered in adopting a formula. Indamines (blue) are well marked intermediate stages in safranine (red) formation. Safranines are obtained by heating indamines with primary monamines; also by oxidation of p-p'-diamido-diphenylamiiie in presence of primary amines, by oxidation of a p-diamine in presence of primary amines, by oxidation of a p-diamine along with a derivative of m-amidodiphenylamine, and by the commercial method of oxidising a molecule of a p-diamine with two molecules of a monamine.
By this last method it is found that the following conditions are essential to obtain a safranine: (i) the p-diamine employed must have one amido group unsubstituted, one molecule of this body being required; (ii) two molecules of the same or different monamines are required, of which one must have the p-position unsubstituted, while in the other it may or may not be substituted, but the amido group itself must be unsubstituted, i.e., a primary amine.
Witt proposed an asymmetrical formula for safranine:
[-]
The dotted cleavage lines show how well it agrees with the main facts of saf Vanine synthesis as laid down above. It has, however, been dropped and the formula proposed by Bernthsen is generally adopted: [-]
1 The asymmetric formula has recently been revived by Barbier and Sisley who stated that the commercial dye is mainly of this type. Their claim however has since been refuted by Hewitt and his collaborateurs who found their oxyaposafranone to be identical with the body obtained from p-nitrosopheuol and m-oxydiphenylamine.It was found that the number of substituted amido derivatives according to the asymmetrical formula could not be prepared. Also m-amido-o'. o'-dinitro-diphenylamine could be condensed with p-phenylene diamine to give a safranine, which is not in accordance with asymmetric substitution. Again, the same phenylsafranine is obtained in two ways: (i) by oxidation of m-amidodiphenylamine along with p-amidodiphenylamine, (ii) by oxidation of m-phenyl-amidodiphenylamine and p-phenylene diamine. These facts are not explained by the asymmetric1 formula but quite agree with the Bernthsen formula. This latter is adapted to express either ortho or para quinone structure. Thus the simple safranine written above may be expressed: [-]
The main trend of evidence is in favour of the o-quinone formula. Safranine is strongly basic, and the base itself is not obtained in the usual way, namely, by alkali treatment of the salt. It may however be obtained by oxidation with silver oxide of the following diphenylamine derivative:
[-]
It is strongly basic, due to the peritavalent nitrogen atom which is an essential part of the ortho quinonoid structure.
The ready reoxidation of the leuco compound of safranine in air agrees also with the general behaviour of o-quinone dyestufFs in this respect. According to the p-quinone formula safranine is an imide. It is actually the case that by ordinary methods of diazotisation only one amido group can be diazotised. When this is done and the diazo body boiled with alcohol aposafranine is obtained which cannot be further diazotised by the general methods.[-]
However, by treatment in strong acid solution (green) this body can be diazotised, and also safranine can be diazotised in both amido groups, and on boiling with alcohol, plienylphenazonium chloride is obtained.
[-]
This body is reconverted into safranine base by treatment with ammonia.
Safranine base may also be obtained by treatment of the sulphate with baryta. It crystallises in green leaflets.
It may further be stated that safranine base on heating can be obtained almost free from oxygen, which is in accordance with the p-quinonoid formula.
[-]
On the other hand certain chlorine substitution products of safranol clearly support the ortho quinone structure.
[-]
The formula for aposafranol may be written from what has been explained above.
The formation of safranine by the oxidation method of synthesis is apparently due to formation of quinone derivatives, by oxidation of the p-diamine used, which then form diphenylamine derivatives by addition of molecules of amines. These diphenylamine derivatives by oxidation give indamines which have again a quinone structure and allow of further addition, giving phenylamidodiphenylamines of the type shown on page 229 from which safranine base is obtained. Further oxidation in presence of acid gives the dyestuffs found in commerce. The whole process bears considerable resemblance to the synthesis of Magenta in respect of the part played by quinone structure. (See p. 191.)
The constitutions of other dyestuffs of the azonium class have been assigned on similar evidence to that discussed above for safranine.
Commercial Safranine (many brands) is obtained by oxidation ,of equal molecules of p-tolylene diamine and o-toluidine (obtained mixed by reduction of amidoazotoluene), to give an indamine. The required extra molecule of monamine is then added, i.e., aniline or o-toluidine. The recovered oils from the Magenta melt are rich in o-toluidine, and may be used for Safranine manufacture. Potassium bichromate in hot acid solution is the oxidising agent. Mauve and other azines are also formed. Chalk is added to precipitate impurities and the dyestuff salted out of the filtrate. The salt of the dyes tuff formed with hydrochloric acid is crystalline.
[-]
Methylene Violet BN, etc. (M.) is the asymmetric ( N(CH3) 2 ) dimethyl-phenyl safranine. Other dyes of this class are Tannin Heliotrope (C.), Rhoduline Violet (By.), Amethyst Violet (K.), etc.
Of the phenyl (C6H8.NH-) safranines or mauveines few are important.
Mauve itself possesses historical interest, being the first of the coal tar dyestuffs. It was obtained by Perkin in 1856 by oxidation of a crude aniline containing mixed toluidines.
[-]
It still finds some small use as a basic dye, mainly on account of its comparatively good fastness to light, which exceeds that of Methyl Violet, on that account it finds some use for blueing or " white-dyeing " of silk.
Indazine M, etc. (C.) is a blue basic dye of the mauve class, as is also Metaphenylene Blue.
Milling Blue (K.) is a sulphonated di-naphthosafranine or rosinduline of the mauve type.
[-]
Magdala Red is a basic dyestuff of the safranine class.
[-]
It is the naphthyl homologue of phenyl safranine. It exhibits fluorescence, and finds a small use on silk.
Certain rosindulines (aposafranine class) are also important, and categorically should have been dealt with before the safranines. A good deal of evidence, analogous to that brought up in discussing the constitution of safranines, has been accumulated in favour of a similar type of formula for rosindulines. The simplest rosinduline is obtainable by condensing 4amido-^-naphthoquinone with o-amido-diphenylamine, whereby two molecules of water are split off, giving the base.
[-]
The rosindulines are sometimes obtained commercially by heating simple azo compounds with α-naphthylamine hydrochloride or aryl-azo-α-naphthylamines with aniline and aniline hydrochloride (i.e., a primary amine), e.g., Induline Scarlet already mentioned is obtained from the azo compound of monoethyl-p-toluidine by melting with α-naphthylamine hydrochloride. Anilidonaphthoquinones and anilineα-naphthylamine are also used to give rosindulines by similar heating methods. The process involves the formation of intermediate bodies analogous to those found in the induline melt (see later). These have been isolated by stopping the melt before completion of the reaction. Thus, by melting benzol azo-α-naphthylamine with aniline and aniline hydrochloride, phenylrosinduline is obtained finally, by intermediate formation of a trianilido quinone:
[-]
This body can be easily prepared in good yield from β-naphthoquinone-4-sulphonic acid by heating with aniline. The first stage is reached in aqueous solution, but the second only by melting.
[-]
This trianilido quinone is a tautomeric form of the intermediate product above written. By further melting with aniline and aniline hydrochloride up to 160°C. phenylrosinduline is obtained. Thus the trianilido quinone [-] by direct condensation gives leuco-phenylrosinduline, which readily oxidises in presence of air to the dyestuff base.
[-]
The excess of aniline is dissolved out of the melt with the required amount of hydrochloric acid and phenylrosinduline filtered off. This product finds commercial use as the disulphonic acid Azocarmine G in paste (B.), which is an acid dyestuff difficultly soluble in water. The monosulphonic acid is first prepared by heating up to 95°C. with oil of vitriol. It is then purified by treatment with caustic soda and washing, and further sulphonated. This intermediate purification results in a better shade in the final product.
Phenylrosinduline hydrochloride is readily dissociated hydrolytically, and is not used as a basic dye.
Azocarmine B (B.) is the trisulphonic acid of phenylrosinduline.
By heating this dyestuff with water at 160° to 180°C. the monosulphonic acid of a rosindone is obtained.
Rosinduline 2G (K.)is the monosulphonic acid of a rosindone.
[-]
Rosinduline G (K.) is a very similar body. These are acid dyestuffs for wool.
Neutral Blue (C.) already mentioned as an isorosinduline is obtained by the action of nitroso-dimethylaniline hydrochloride on phenyl-β-naphthylamine.
Indulines. - This class includes blue, violet and blue-black dyestuffs obtained by heating amidoazobenzene with aniline and aniline hydrochloride to the boiling point, or under pressure. Almost any azo or nitroso compound on treatment in this way will give indulines. If p-phenylene diamine be added, basic indulines are obtained. The usual products are insoluble in water but soluble in alcohol, and on sulphonation give water-soluble acid dyes.
It has been found that the formation of quinone anilides plays an intermediate role in induline synthesis. Thus azophenine has been isolated and identified by stopping the melt and extracting with alcohol. It forms dark red crystals of formula [-]
The changes involved in the formation of this body from amidoazobenzene are probably of the following type:
[-]
The removal of two H atoms as required for the final stage of this process, appears to be accomplished by reduction of a certain amount of amidoazobenzene, which would account for the presence of some p-phenylenediamine found in the melt.
Quinone anilides of the azophenine type readily condense further on raising the temperature from 100° to 130°C. thus: [-]
The process of induline formation should be compared with that of rosinduline synthesis already described.
Further heating results in the introduction of more anilido groups.
The following are well known members of the induline class obtained by more or less modified processes, similar to the one described:
Indamine Blue (M.). A basic dye used instead of indigo.
[-]
Other Indamine Blue brands are obtained by heating nitroso-dimethylaniline with o- or p-toluidine.
Induline B, 3B, etc. (many brands). The spiritsoluble brands are hydrochlorides of the same type as Indamine Blue above and of the following bases:
[-]
The water-soiuble acid dyes are obtained by sulphonation of spirit-soluble indulines. Various Fast Blues, Printing Blues, Acetine Blues, etc., are of this type. Besides being acid dyestuffs suitable for wool and silk, they possess residual basic properties allowing of fixation on tannin-mordanted cotton.
Nigrosines are obtained by heating nitrobenzene with aniline and aniline hydrochloride in presence of metallic iron (filings) to 180°C. Nitrosophenol also gives dyes of this class when heated with aniline and aniline salt. They are used for pigments, shoe polishes, etc. The water-soluble acid dyes of this class are obtained by sulphonation of the blue-black or black nigrosine bases.
Aniline Black. In 1834 Runge obtained insoluble black compounds by oxidation of aniline with chromic acid. A similar precipitate was obtained by Perkin in making Mauve. It was not applied in dyeing till 1862, when Calvert obtained a fast black on cotton by oxidation of aniline in contact with the cotton fibre. Aniline black is largely produced in this way, and itself is not a commercial dyestuff.
There are three chief methods in use: (1) the socalled single-bath black is used for cotton hanks, which are treated with a cold mixed solution of aniline, potassium bichromate and sulphuric acid. Later the temperature is gradually raised. A large amount of black is precipitated in the bath and a considerable quantity of chrome is deposited on the fibre as well as aniline black itself. (2) The so-called "aged" or oxidation black is applied to cotton by padding with a solution containing aniline, aniline salt, potassium chlorate and a copper salt, the latter acting as oxygen carrier. The dried material is then "aged" in a warm moist chamber and becomes green, due to formation of emeraldine. It is given a bath of bichromate to complete the oxidation of emeraldine to aniline black. Attempts have been made to overcome the tendering of cotton in this process by replacement of the chlorate by air oxidation in presence of a trace of a catalyser, e.g., p-phenylene diamine. (3) The steam black can be reserved, and is used in calico printing. The paddingliquor contains aniline salt, potassium chlorate and ferrocyanide, and by printing on a thickened alkaline paste after drying the development of aniline black is prevented from taking place under the reserve paste in the subsequent steaming.
All these processes show similar stages in aniline black formation, namely, first a green compound called emeraldine, then a blue-black body turned green by sulphur dioxide or mineral acids. This base has been called nigraniline or greenable black. Finally, ungreenable aniline black or pernigraniline is obtained, which is not aftected by sulphur dioxide or boiling with dilute mineral acids, and is a very stable body. On reduction it gives an almost colourless leuco body which re-oxidises in air, and on oxidation a very good yield of p-benzoquinone. Complete reduction or distillation with zinc dust gives para diamines and amido-diphenylamines. The recent researches of Willstaetter and Green and their collaborateurs have increased the knowledge of aniline black. The first stage in the oxidation of aniline is the formation of phenyl quinone di-imide [-] a yellow body which polymerises in presence of acids to give emeraldine C24H20N4. Further oxidation of this base gives a red compound which it is claimed by Willstaetter can polymerise to give finally aniline black. Green thinks Willstaetter's products are not those obtained in the commercial production of aniline black. The lengthy indamine formula deduced from polymerisation would not possess the stable properties of aniline black. Finally, analyses of aniline black vary, no doubt due to the black product consisting of mixtures of nigraniline with pernigraniline, some free aniline is necessary to get the fully formed black by oxidation of nigraniline, according to Green.
It has long been recognised that aniline black shows great similarity to the azines both in method of formation and properties. A considerable difficulty, however, has been experienced in the fact that the degradation products obtained from aniline black contain no ortho derivatives. The trend of evidence is in the main towards an azine structure for aniline black, to which Green has ascribed the following formula: [-]
- See Jour. Soc. Dyers, contributions by A. G. Green and others, pp. 105 and 338, 1913. Also Aniline Black, Noelting and Lehner. -
Diphenyl Black Base P (M.) consists of amidodiphenylamine and on oxidation gives an aniline black. Diphenyl Black Oil DO (M.) is a mixture of the base and aniline. The use of these bodies demands less strong oxidation on the fibre, and therefore reduces the risks of tendering the fabric.
Paramine Brown is a chocolate brown produced on the fibre from p-phenylene diarnine in a similar way to the production of aniline black. The diamine is sold for fur dyeing, etc., as Ursol D (Ber.), Furreïn D (J.), etc. Other Ursol and Furreïn dyeings are produced by por m-amidophenol. The Furrole (C.) and Nako (M.) colours belong to the same class.
Oxazine Dyestuffs. - These dyestuffs are derivatives of diphenoxazine, which is obtained by condensing o-diamidophenol with pyrocatechin.
[-]
By introducing auxochrome groups into this body leuco oxazine dyestuffs are obtained which oxidise in air to give the dyestuffs. The class exhibits great similarity to the azines in most respects. They are prepared from o-hydroxy derivatives of in dam in es or indophenols, or with these bodies as intermediate stages involved in their production. The various methods of i ml; miine synthesis may be employed to reach this stage, further condensation taking place readily on heating, by quinone change; e.g., nitrosodimethylaniline and resorcin give
[-]
This is produced on the cotton fibre by printing with a paste containing resorcin and the nitroso body with tannin as mordant. The cloth is dried and steamed; the indamine winch is first formed condenses further to give Nitroso Blue or Resorcine Blue:
[-]
It will be noted that the adoption of an o-quinonoid formula for oxazine dyestuffs demands the assumption of tetravalent oxygen.
The first commercial dyestuff of this class was Naphthol Blue D. R. New Blue R or Meldola's Blue discovered in 1879 by Meldola. It is obtained by adding gradually nitrosodimethylaniline hydrochloride to β-naphthol dissolved in its own weight of glacial acetic acid, or three times its weight of alcohol, the temperature being maintained at 110°C. under reflux condenser. The reaction is violent at first. The pure dyestuff may be separated with alcohol, but it is usually crystallised out as the double chloride with zinc. It is used for cheap indigo blue shades on tanninmordanted cotton.
[-]
By further action of excess of nitrosodimethylaniline New Blue B is obtained.
[-]
If, instead of β-naphthol, in making Meldola's Blue, 2.7-dioxynaphthalene be used, Muscarin is obtained.
Other basic dyestuffs of this class are obtained similarly thus:
Capri Blue GON (By.), nitrosodimethylaniline and dimethyl m-amidocresol.
New Methylene Blue GC (C.), dimethylamine and Meldola's Blue, and subsequent oxidation.
[-]
Nile Blue A (B.), nitrosodiethyl-m-amidophenol and α-naphthylamine.
[-]
Using benzyl-α-naphthylamine in the above condensation, one gets Nile Blue 2B (B.).
Fast Black (L.) is obtained by action of nitrosodimethylaniline on m-oxydiphenylamine.
Beside the above basic dyestuflfs some important mordant dyes belong to this group.
By acting on gallic acid in boiling methyl alcohol solution with nitrosodimcthylaniline hydrochloride, Gallocyanine (many brands) is obtained.
[-]
It gives violet blue chrome lakes, and is extensively used on wool and in calico printing. Certain brands (powder) are bisulphite compounds. On heating with aniline, followed by sulphonation, it gives Delphin Blue B (By.), an acid mordant dyestuff, the -COOH group being replaced by -NH-C6H4-SO3 NH4.
Modern Blue, Modern Cyanine, Indalizarin, Prune, etc., are Gallocyanine derivatives.
Prune pure (S.) is obtained by using, instead of gallic acid (-COOH), the methyl ether (-COOCH3).
Gallamine Blue paste (By., G.) is obtained by using gallamide (-CO NH2) instead of gallic acid (COOH).
Gallanil Violet (D.H.) is obtained by use of the anilide of gallic acid (-CO.NH.C6H5).
Corein is the diethyl analogue of Gallamine Blue.
There are many others of this class.
The oxy-derivatives of the oxazine class corresponding to safranones are of no commercial value.
Thiazine Dyestuffs. - These are closely allied to the azine and oxazine groups. They contain one atom of sulphur, which is regarded as tetravalent in the o-quinonoid formula. Lauth's violet was the earliest known colouring matter of this class. It was obtained in 1876 by oxidation of p-phenylene diamine with ferric chloride in acid solution in presence of sulphuretted hydrogen. The violet thus obtained has no commercial value, but substitution of dimethyl-p-phenylene diamine for the simple diamine by Caro gave Methylene Blue. The constitution of the thiazines has been largely built up from the work of Bernthsen on these two dyestufls. He nitrated thiodiphenylamine, obtained by heating diphenylamine with sulphur, and on reduction obtained the leuco base of Lauth's violet which oxidised in presence of air to give the dyestuff.
[-]
Hence also the constitution of Methylene Blue: [-]
Bernthsen devised a new and cheaper synthesis of this dyestuff. Nitrosodimethylaniline i reduced with iron filings, and the resulting solution of dimethyl-pphenylene diaiume is oxidised in dilute acid solution with bichromate, in presence of sodium thiosulphate. A thiosulphonic acid is formed: [-]
This body can be obtained as white crystals, but is never isolated from solution in the manufacture of Methylene Blue. An extra molecule of dimethylaniline is added, and with further oxidation gives an indamine thiosulphonic acid.
This greenish blue body on boiling with zinc chloride solution gives the dyestuff, by first losing ELSO 4 , and the leuco-azine thus formed oxidises rapidly in air, or in presence of the acid oxidising agent. The dyestuff is put out commercially as a double chloride with ZnCl2.
[-]
Methylene Blue is largely used on tannin-mordanted cotton and as a basic "topping" colour, i.e., for brightening up other shades. It is faster to light than most basic dyes. It .is used as a stain in microscopy, and as free base finds internal use as a medicine.
New Methylene Blue N, GB, R, etc. (C.) is obtained when mono-ethyl-o-toluidine is used as in the synthesis last described.
[-]
Certain brands of this name are oxazines, see p. 243.
Methylene Green (many brands) is obtained by nitration of Methylene Blue with sodium nitrite and hydrochloric acid.
[-]
It is not known for certain to which nucleus the o-quinonoid bonds should be attached.
Thionine Blue O, B, etc. (M., By.) is the trimethylethyl product analogous to Methylene Blue (a tetramethyl product) and is similarly prepared.
The above are all basic dyestuffs. The only acid dyestuff of outstanding interest belonging to this class is Thiocarmine R (C.). This dyestuff is made by a thiosulphonic acid process, similar to that described for Methylene Blue, using p-amidoethylbenzylaniline sulphonic acid as starting point.
[-]
The thiosulphonic acid of this body is oxidised to form an indainine with ethylbenzylaniline sulphonic acid, which gives finally a blue acid dye:
[-]
There are several important acid-mordant dyes of the thiazine class.
Indochromogen S (S.) is obtained by condensation in dilute alkaline solution of p-amidodiethylaniline thiosulphonic acid with 1.2-naphthoquiiione-4.6-disulphouic acid.
[-]
It gives blue shades on a chrome mordant.
Brilliant Alizarin Blue G, R, etc. (By.) is obtained by a similar method and is the dimethyl body corresponding to Indochromogen S (diethyl). Sulphobenzyl ethyl-p-phenylene diamine and analogous compounds give similar dyestuffs.
- Additional information may be obtained from sections of Thorpe's Dictionary of Applied Chemistry, where may also be found patent references, etc. -
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