Yellowing of paper

Carter, Hemy A. (1996). The Chemistrjr of Paper Preservation. Part 2 The Yellowing of Paper and Conservation Bleaching. yowrwa/ of Chemical Education 73(11) 1,068-1,073. 

Yellowing of paper under UV irradiation is a result of photo-oxidation of hemicellulose, which includes xylan and glueomanan [773, 981, 1859]. A seven-line ESR spectrum has been recorded during UV irradiation of xylan [968]. The photolytic chain scission of hemicellulose may occur either at the end of the molecule or in the middle of the chain. Hemicellulose can yield monosaccharides after photoirradiation, followed by transformation into coloured materials. 

A second degradation process is oxidation, often photo-induced especially by exposure to light not filtered for uv. The radicals resulting from this reaction promote depolymerization of the cellulose, as well as yellowing and fa ding of paper and media. Aging causes paper to become more crystalline and fragile, and this can be exacerbated particularly if the paper is subjected to poor conditions. 

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. 

On a clean sheet of paper, use a sharp pencil to trace the angle formed by the two sticks connecting the yellow (hydrogen) balls to the black (carbon) ball. 

FIGURE 7.6 A representation of the absorption of visible light by a sheet of paper, resulting in the paper having a red color. The following abbreviations are used vi = violet, bl = blue, gr = green, yl = yellow, or = orange, and re = red. 

In the pulp and paper industry, UV-vis spectroscopy proves helpful in answering many related questions (e.g. around yellowing of pulp), Kappa number monitoring,alkyl xanthate decomposition, etc. 

Both TATP and HMTD have been applied by terrorist groups worldwide in the production of homemade detonators. TATP is, however, seen in more instances. Examples of improvised caps can be seen in Figure 3.10. The photograph gives an illustration of the standard paper detonators (in this case produced from yellow lined paper and Christmas tree bulbs) and also shows a variety produced from syringes. The detonators in the photograph were recovered in Amman, Jordan. 

Ink Printing,—By means of tine process, positive printe may be obtained in common writing ink. A ijheot of paper is immersed in a nearly saturated solution of bichromate of petassa", and dried. It Is then exposed under a negetive to sunshine for a low mitmtes. Where the light acts the bichromate is reduced, and a brown positive upon a yellow ground, obtained. This is well... 

YELLOW TURMERIC INDICATOR PAPER TURNS BROWN WITH BORIC ACID. YELLOW COLORING MATTER IN TABLE MUSTARD IS TURMERIC. TO MAKE TEST PAPER, DIP STRIPS OF PAPER TOWELING IN MUSTARD. WASH MUSTARD OFF. DRY STRIPS. 

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