Color of paper

Diphenylmethane Dyes. The diphenyhnethane dyes aie usually classed with the tiiaiyhnethane dyes. The dyes of this subclass are ketoimine derivatives, and only three such dyes are registered in the Colour Index. They ate Auramine O [2465-27-2J Cl Basic Yellow 2 (Cl 41000) (21, R = CHg), Auramine G [2151 -60-2] Cl Basic Yellow 3 (Cl 41005) (22), and Cl Basic Yellow 37 [6358-36-7] (Cl 41001) (21, R = C2H5). These dyes are still used extensively for the coloration of paper and in the preparation of pigment lakes. 

These are defined as anionic dyes with substantivity for cellulosic fibres applied from an aqueous dyebath containing an electrolyte. The forces that operate between a direct dye and cellulose include hydrogen bonding, dipolar forces and non-specific hydrophobic interaction, depending on the chemical structure and polarity of the dye. Apparently multiple attachments are important, since linearity and coplanarity of molecular structure seem to be desirable features (section 3.2.1). The sorption process is reversible and numerous attempts have been made to minimise desorption by suitable aftertreatments (section 10.9.5). The two most significant non-textile outlets for direct dyes are the batchwise dyeing of leather and the continuous coloration of paper. 

Direct dyes have only modest fastness to washing, which may be improved by after-treatments such as metal-complex formation (section 5.5.3) or by diazotisation of the dye on the fibre and further coupling of the diazonium salt with an insoluble coupling component (section 1.6.14). In addition to their use on cotton and viscose, direct dyes are important in the dyeing of leather. The cheapest members of this class are also used in the coloration of paper, since for this purpose fastness properties are largely irrelevant and price is all-important. 

Organic pigments are used to color a variety of media. It is useful to distinguish between three primary fields of application the coatings and paints industry, the printing inks industry, and the plastics and fibers industry. Besides, organic pigments are used for special purposes, for instance in office materials and in the mass coloration of paper. 

P.R.17 provides medium reddish shades. As a result of poor fastness properties, its commercial significance is somewhat limited and it is sold only in small volume. P.R.17 has the advantage of being fast to acid, alkali, and soap. It is therefore used in offset, gravure, and flexo printing inks wherever tolerance to alkali and soap is a major concern. Moreover, P.R.17 is also employed in connection with mass coloration and surface coloration of paper. 

Elemental composition Na 58.93%, S 41.07%. An aqueous solution is analyzed to determine sodium content. Also, an aqueous solution may be analyzed for sulfide by methylene blue colorimetric test or by iodometric titration (APHA, AWWA, and WEF. 1999. Standard methods for the Examination of Water and Wastewater, 20 ed. Washington, DC American Pubhc Health Association). The methylene blue test is based on reacting sulfide, ferric chloride and dimethyl-p-phenylenediamine to produce methylene blue. Also, sulfide can be measured by using a sdver-sdver sulfide electrode. Quahtatively, sulfide may be identified from the hberation of H2S on treatment with acid. The H2S turns the color of paper soaked with lead acetate black (See Hydrogen Sulfide). 

An alternative way of classifying dyestuffs is by their application areas, but as there is large overlap between product structural classes and their uses, it is less satisfactory. However, from a commercial standpoint it is the application method that determines the potential of a dyestuff and the reason for its industrial manufacture and sales. In this section the different application methods will be described mainly in relation to the end use, e.g. the dyeing or printing of cotton and other fibres, the coloration of paper or leather, the use in food and cosmetics etc. 

Di- and Triaryl Carbonium and Related Dyes. As a class, these dyes are bright and strong, hut are generally deficient in lightfastness. Consequently, they are used in outlets where brightness and cost-effectiveness. rather than permanence, arc paramount, for example, the coloration of paper. Many dyes of this class, especially derivatives of pyronines Ixamhcnes). arc among the most fluorescent dyes known. 

A variety of colors of paper (all 12 colors of the color wheel, plus white, black, and gray) pencil ruler scissors glue or rubber cement typing paper or other paper suitable for mounting samples. 

For this reason many, and above all the older, acid dyes have lost all importance for the dyeing of wool and are used today only for the coloring of paper, soaps, food, and cosmetics. 

Coloring of paper pulp is a problem which requires further study. As mentioned previously, most coloring agents used in commercial paper manufacture are easily faded by light. Many cannot be used under conditions of neutral pH. Those conservators fortunate enough to have... 

In these early years, Heuser wrote chapters for various texts and monographs, on such varied subjects as paper pulp and artificial silk, the coloring of paper on paper-machines, celluloid and various cellulose films, methods of determining furfural, and xylan. 

Cut three paper disks about 7 cm in diameter for each of the elements Li, S, Mg, O, Ca, N, Al, and I. Use a different color of paper for each element. Write the symbol of each element on the appropriate disks. 

The optical behavior of papers under filtered light examination and ultraviolet (UV)-visible (or visible-infrared (IR)) luminescence is also an important characteristic that helps to differentiate them. Absorption spectroscopy can be used to measure and compare the color of papers. 

Chekunina, L. L Danilova, D. A. Polovinkin, V. L. Replacement of direct dyes during the coloring of paper. Bumazhnaya Promyshlennost 1975, 15-16 Chem. Abstr. 1975, 83, 149385. 

Kielhorn-bayer, S. Kuehn, I. Tresch, R. Aqueous, dye-containing, polymer-based compositions for coloring of paper. Ger. Offen. DE 19937261, 2001 Chem. Abstr. 2001,134, 164727. 

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