Sulphur dyes properties

Chemical properties. A chlorine atom ortho or para to a nitro group is especially reactive and is readily substituted. Numerous examples of such reactions, utilized in the preparation of explosives, are given later in the descriptions of preparation methods for dinitrophenol, dinitroanisole, hexanitrodiphenylamine, hexanitro-diphenyl sulphone, dinitroaniline, tetryl, etc. Chlorodinitrobenzene reacts with sodium sulphide and sulphur to yield sulphur dyes. The action of sodium disulphide results in the formation of tetranitrodiphenyl sulphide (p. 554). 

In their reduced state their dyeing properties resemble in many respects those of the direct dyes. They exhaust better in the presence of electrolytes and vary considerably with regard to the temperatures at which maximum e.xhaustion takes place. They are decomposed by acids, usually with the liberation of hydrogen sulphide and the precipitation of insoluble decomposition products. On exposure to air, or when acted upon by mild oxidizing agents, a portion of the sulphur is oxidized to sulphuric acid. 

The water-soluble sulphur dyes will dissolve in water without any other addition, but it must be emphasized that this solution will not dye cellulose without the addition of sodium sulphide and carbonate. Their advantages are that they are easier to handle, contain less insoluble matter, making them more attractive for package dyeing, and they possess superior levelling properties. 

Sulphonic acids are water soluble, viscous liquids. Their acidity is akin to that of sulphuric acid feey form salts with bases but fail to undergo esterification with alcohols. Their properties vary according to the nature of R some are prone to thermal decomposition. They are used as surfactants and in the dye industry some have biological uses. 2-Amino-ethanesulphonic acid is the only naturally occurring sulphonic acid. 

Cl Sulphur Black 1, which is produced from the relatively simple intermediate 2,4-dinitrophenol and aqueous sodium polysulphide. A similar product (Cl Sulphur Black 2) is obtained from a mixture of 2,4-dinitrophenol and either picric acid (6.148 X = N02) or picramic acid (6.148 X = NH2). A black dye possessing superior fastness to chlorine when on the fibre (Cl Sulphur Black 11) can be made from the naphthalene intermediate 6.149 by heating it in a solution of sodium polysulphide in butanol. An equivalent reaction using the carbazole intermediate 6.150 gives rise to the reddish blue Cl Vat Blue 43 (Hydron blue). This important compound, which also possesses superior fastness properties, is classified as a sulphurised vat dye because it is normally applied from an alkaline sodium dithionite bath. Interestingly, inclusion of copper(II) sulphate in the sulphurisation of intermediate 6.150 leads to the formation of the bluish black Cl Sulphur Black 4. 

Groups which do not themselves produce explosive properties, but may influence them in the same way that auxochromic groups vary the colour intensity and shade of a dye, are called auxoplosives by these authors. We may quote hydro-XY, carboxyl, chlorine, sulphur, ether, oxygen, amine, etc. as examples of such groups. 

Nearly all azo-dyestuffs give characteristic colour-reactions on dissolving in strong sulphuric acid, and it is probable that in such cases the basic properties of the azo-group become apparent by the action of the strong acid. It is worthy of notice that most substituted azo-dyes give the same reaction with sulphuric acid as the... 

Metaxylidine gives similar compounds if treated with sulphur. One of these, M.P. 107°, possesses one amido-group capable of being diazotised, and certain of the azo-dyes prepared with it form the various brands of Erica. These dyestuffs have the remarkable property of dyeing cotton from a bath containing sulphate of soda, producing pleasing pink shades of considerable fastness. 

This dyestuff is prepared by heating -nitroalizarin with glycerine and sulphuric acid. It is peculiar in so far that it possesses the lake-forming properties characteristic of the alizarin dyes, and is at the same time a weak base. Alizarin blue was discovered by Prud homme [28], and the determination of its constitution by Graebe [29] led to the synthesis of quinoline by Skraup from glycerine, nitrobenzene, and aniline. 

Sulphur-containing polymethine dyes, including those incorporating thiazolidine and benzothiazole residues, exhibit certain anomalous chromophoric properties (e.g. abnormal vinylene shifts), which have been traced to an interannular non-bonded S-S interaction in the monomethine ion. The conclusion is supported both by a detailed examination of the... 

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