Dyes, water soluble

An emulsion may be defined as a mixture of particles of one liquid with some second liquid. The two common types of emulsions are oil-in-water (O/W) and water-in-oil (W/0), where the term oil is used to denote the water-insoluble fiuid. These two types are illustrated in Fig. XIV-1, where it is clear that the majority or outer phase is continuous, whereas the minority or inner phase is not. These two emulsion types are distinguished by their ability to disperse oil or water-soluble dyes, their dilution with oil or water, and their conductivity (O/W emulsions have much higher conductivity than do W/0 ones see Ref. 1 for reviews). 

The FD C certified colors are all water-soluble dyes, but can be transformed into insoluble pigments known as lakes by precipitating the dyes with alurninum, calcium, or magnesium salts on a substrate of aluminum hydroxide. The lakes are useful in appHcations that require color whereas in dry form, such as cake mixes, or where water may be present and bleeding is a problem, such as food packaging. FD C Red Lake No. 3 was deHsted in Febmary... 

Phthalocyanine Dyes. In addition to their use as pigments, the phthalocyanines have found widespread appHcation as dyestuffs, eg, direct and reactive dyes, water-soluble dyes with physical or chemical binding, solvent-soluble dyes with physical or chemical binding, a2o reactive dyes, a2o nonreactive dyes, sulfur dyes, and wet dyes. The first phthalocyanine dyes were used in the early 1930s to dye textiles like cotton (qv). The water-soluble forms Hke sodium salts of copper phthalocyanine disulfonic acid. Direct Blue 86 [1330-38-7] (Cl 74180), Direct Blue 87 [1330-39-8] (Cl 74200), Acid Blue 249 [36485-85-5] (Cl 74220), and their derivatives are used to dye natural and synthetic textiles (qv), paper, and leather (qv). The sodium salt of cobalt phthalocyanine, ie. Vat Blue 29 [1328-50-3] (Cl 74140) is mostly appHed to ceUulose fibers (qv). 

Lakes are either dry toner pigments that are extended with a soHd diluent, or an organic pigment obtained by precipitation of a water-soluble dye, frequendy a sulfonic acid, by an inorganic cation or an inorganic substrate such as aluminum hydrate. 

Another cosmetic appHcation of aluminum compounds is as lakes for Hpstick manufacture (21). A water-soluble dye can become a Hpstick ingredient if combined with compounds that are colorless and insoluble. The result, caHed a lake, is insoluble in both oil and water. Some dyes are laked with alumina others are dissolved in water and treated with solutions that precipitate Al(OH)2 with the dye molecules occluded in the precipitate. These... 

Hydrophobic fibers are difficult to dye with ionic (hydrophilic) dyes. The dyes prefer to remain in the dyebath where they have a lower chemical potential. Therefore nonionic, hydrophobic dyes are used for these fibers. The exceptions to the rule are polyamide and modified polyacrylonitriles and modified polyester where the presence of a limited number of ionic groups in the polymer, or at the end of polymer chains, makes these fibers capable of being dyed by water-soluble dyes. 

Other New Methods. Because the values obtained are dependent on the conditions of measurement, standard test procedures are under review by ISO for determination of cold-water solubiUty of water-soluble dyes (38) determination of the solubiUty and solution stabiUty of water-soluble dyes (39) and determination of the electrolyte stabiUty of reactive dyes (40). 

Both acids and alkalis will adversely affect the material. Strong alkalis and acids will cause decomposition. The water absorption is high and consequently casein is easily stained. As a corollary to this it may be dyed without difficulty. Acidic and basic water-soluble dyes are normally used. Typical properties of casein plastics are given in Table 30.2. 

Although the substitution of a preformed phthalocyanine always leads to a complex mixture of more- or less-substituted products, the reaction is of major industrial importance. Besides the chloro- and bromocopper phthalocyanines, also polysulfonated phthalocyanines, which are used as water-soluble dyes, are produced by the reaction of copper phthalocyanine with the respective reactant. While typical aromatic reactions of the Friedel-Crafts type are also possible,333 direct nitration of the macrocycle commonly results in oxidation of the phthalocyanine. However, under mild conditions it is possible to introduce the nitro group directly into several phthalocyanines.334... 

In a typical acid—base titration, the analyte is a solution of a base and the titrant is a solution of an acid or vice versa. An indicator a water-soluble dye (Section J), helps us detect the stoichiometric point, the stage at which the volume of titrant added is exactly that required by the stoichiometric relation between titrant and analyte. For example, if we titrate hydrochloric acid containing a few drops of the indicator phenolphthalein, the solution is initially colorless. After the stoichiometric point, when excess base is present, the solution in the flask is basic and the indicator is pink. The indicator color change is sudden, so it is easy to detect the stoichiometric point (Fig. L.3). Toolbox L.2 shows how to interpret a titration the procedure is summarized in diagram (3), where A is the solute in the titrant and B is the solute in the analyte. 

The penetration of ions from the subphase into the shell of spread particles is a general phenomenon and can be used to modify and functionalize the particle surface. For example, metal ions, such as Ba and Fe, or cationic polyelectrolytes, such as the polycation of polyallylamine, can be adsorbed at anionic particles, while anionic water-soluble dyes, such as phthalocyanine tetrasulfonic acid and 1.4-diketo-3.6-diphenylpyrrolo[3.4-c]pyrrole-4, 4 -disulfonic acid (DPPS) [157], can be adsorbed at cationic particles. However, since only a monolayer of the dye is adsorbed, a deep coloration of the particles is not obtained unless a dye with very high absorption coefficient is used [156],... 

The oil phase included a fatty acid, a fatty alcohol and hydrocarbons. The emulsion had a pH of 5.1 to 5.4, exhibited emulsion and pH stability at 37 for at least 21 days, and was shown to be an oil-in-water type by being readily dispersible in water and by its uptake of a water-soluble dye. In inhibition... 

Figure 10.12 Examples of water-soluble dyes used in ink-jet printing...

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. 

Kool and co-workers recently reported a multicolor set of water-soluble dyes synthesized through the combination of three to five individual fluorophores assembled on a DNA-like backbone [94, 95]. As a continuation of their previous works on various DNA analogs [96-99], they synthesized the oligodeoxyfluoro-side (ODF) with seven fluorescent monomers, such as pyrene, perylene, dimethy-laminostilbene, and three stilbene derivatives, and they assembled these fluorescent DNA monomers into oligofluor chains using a DNA synthesizer (Fig. 26). Using... 

Another important class of pigment are the so-called toner pigments. These are water-soluble dyes containing sulfonic acid groups which are insolubilized by forming a salt with a divalent cation such as calcium and barium5 (Scheme 2). Until recently the toner pigments were perceived merely as insoluble salts but X-ray studies have shown them to exist as supramolecular metal complexes (see Section 9.12.4.2). 

The most important 2 1 metal complex azo dyes are the 2 1 Cr3+ dyes. These may be symmetrical dyes, such as the water-soluble dye Cl Reactive Brown 10 (28), and the solvent-soluble dye Cl Solvent Yellow 21 (29), used in varnishes as a wood stain. They may also be unsymmetrical complexes, such as Cl Acid Violet 121 (30), used for dyeing wool and nylon. 

Boron complex azo dyes have also been reported. These include solvent soluble boron complexes, such as the red dye (32) used for dyeing polyester and coloring plastics25,26 and water-soluble dyes for the detection of boron (as boric acid) by a color change27 (Scheme 5). 

Divalent metal cations such as Ca2+ are used in some inkjet media, such as coated paper and glossy photorealistic media, to fix the water-soluble dye and make it waterfast by forming an insoluble salt. However, cationic organic compounds are currently the preferred choice for this function. 

Churchley JH, Greaves AJ, Hutchings MG, James AE, Phillips DAS (2000) The development of a laboratory method for quantifying the bioelimination of anionic, water-soluble dyes by a biomass. Water Res 34 1673-1679... 

The high visibility of water-soluble dyes released to the environment ensures that only extremely low concentrations in watercourses would not be noticed. A typical visibility limit in a river would be about 0.1 to 1 mg/1, but this varies with the colour, illumination and degree of clarity of the water. The human eye can detect a reactive dye concentration as low as 0.005 mg/1 in pure water, particularly in the red to violet hue sector [88]. There is considerable debate, however, about what level of environmental hazard is represented per se by colour in effluent. The view has been expressed that dyestuffs should not be regarded as water pollutants because at concentrations of the same order of magnitude as these visibility limits their harmful effects are negligible [89]. Nevertheless, even though this colour problem is mainly if not entirely an aesthetic one, the fact is that the general public will not tolerate coloured amenity water and the problem therefore has to be addressed and rectified [90,91,92],... 

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