Sulphur dyes water soluble

The phthalocyanines must be suitably dis-p>ersed to be used as pigments or they can be sulphonated to water-soluble forms for dyeing and for precipitation as lakes. The dispersion is carried out by solution in sulphuric acid, followed by precipitation in water. 

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. 

Electrolytes are used to promote the exhaustion of direct or reactive dyes on cellulosic fibres they may also be similarly used with vat or sulphur dyes in their leuco forms. In the case of anionic dyes on wool or nylon, however, their role is different as they are used to facilitate levelling rather than exhaustion. In these cases, addition of electrolyte decreases dye uptake due to the competitive absorption of inorganic anions by the fibre and a decrease in ionic attraction between dye and fibre. In most discussions of the effect of electrolyte on dye sorption, attention is given only to the ionic aspects of interaction. In most cases, this does not create a problem and so most adsorption isotherms of water-soluble dyes are interpreted on the basis of Langmuir or Donnan ionic interactions only. There are, however, some observed cases of apparently anomalous behaviour of dyes with respect to electrolytes that cannot be explained by ionic interactions alone. 

With a few exceptions, sulfur dyes are used for dyeing cellulosic fibres. They are insoluble in water and are reduced to the water-soluble leuco form for application to the substrate by using sodium sulfide solution. The sulfur dye proper is then formed within the fiber pores by atmospheric or chemical oxidation. Sulfur dyes constitute an important class of dye for producing cost-effective tertiary shades, especially black, on cellulosic fibers. One of the most important dyes is C.I. Sulphur Black 1, prepared by heating 2,4-dinitrophenol with sodium polysulfide. 

Water-Soluble Sulfur Dyes (C.I. Solubilised Sulphur). Water-soluble sulfur dyes are available in the form of Bunte salts (.S -arylthiosulfuric acid salts) of sulfur dyes and can be dissolved in hot water. The addition of alkali and reducing agent gives them an affinity for the fiber. If NaSH or another reducing agent is used, alkali must be added to trap H+ ions resulting from reduction. 

The sulphur dyes resemble the vat dyes in that they are insoluble in water but reduce to a soluble form which readily reverts to the original state on oxidation. In many cases this reversible change is accompanied by an alteration of colour. Sodium sulphide is the reducing agent commonly used, but in some cases sodium hydrosulphite maybe substituted, making it possible to dye selected vat and sulphur dyes together. 

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. 

The lack of affinity of many of the water-soluble sulphur dyes for cellulose can be of assistance in dyeing tightly-woven piece goods or packages. The method consists essentially of impregnating the material with the dye solution and then exhausting, thus virtually dyeing in situ. 

Sulphation of castor oil with sulphuric acid or oleum yields an easily water-soluble or dispersible sulph(on)ated castor oil also called Turkey red oil, one of the first synthetic detergents, which has been used for textile dyeing, softeners and metal working. ... 

Sulphur. Sulphur dyes are of indeterminate structure and are derived from the sulphurization at elevated temperatures of certain aromatic compounds, e.g. 4-aminophenol (4-amino-1-hydroxybenzene). They are water-insoluble but are rendered soluble for dyeing purposes by sulphide reduction (vatting), reoxidation occurring on the fibre on contact with air. They are all vat dyes. 

Sulfur Dyes (C.I. Sulphur). Two types of sulfur dyes exist amorphous powders, which are insoluble or partially soluble in water. They must be brought into solution by reduction with sodium sulfide, according to Equation (5). 

Di-phenyl amine crystallizes from ligroin in white leaflets with faint odor melting point 54°, boiling point 302 . It is soluble in alcohol, ether and benzene and slightly soluble in water. A solution of diphenyl amine in sulphuric acid, i.e., di-phenyl amine sulphate, is colored blue by a trace of nitric acid, and is used as a test for nitrates. In the color industry di-phenyl amine makes azo dyes. 

This compound is known as sulphanilic acid. It may also be considered as an amino aderivative of benzene sulphonic acid, i.e.j para-amino benzene sulphonic acid. Its name, sulphanilic acid, is in agreement with its relation to aniline and sulphuric acid. It is distinctly different from sulphonic acids of the hydrocarbons in being difficultly soluble in cold water. As we shall see later, it is of great importance in the preparation of dyes. It is a crystalline compound soluble in alkalies as the alkali salt, but is precipitated as the free acid on acidifying the solution of the salt. 

The dyes from diazo-compounds of the benzene series (Pon-ceaux R, RR, RRR, and Coccinines) form scarlet powders, which dissolve in strong sulphuric acid with a red colour. They give crystalline calcium salts which are soluble in hot water. Dyestuffs containing naphthalene rests on both sides dissolve in sulphuric acid with blue or violet colour. 

The characteristic feature of the dyes of this class is that they all contain sulphur linkages within their molecules. They are usually insoluble in water, but dissolve in a solution of sodium sulphide to which sodium carbonate may or may not be added. The sodium sulphide acts as a reducing agent, severing the sulphur linkage and breaking down the molecules into simpler components which are soluble in water and substantive towards cellulose. 

Blue V 7n of.—Sulphate of copper. A salt formed by sulphuric acid in combination with copper. It is soluble in cold or warm water, used much in dyeing and exciting galvanic batteries. 

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