The Use of Color

Any product that depends on aesthetics for consideration for purchase and use will be improved by the use of color. Hence, many ceramic products, such as tile, sanitary ware, porcelain enameled appHances, tableware, and some stmctural clay products and glasses, contain colorants. 

This proliferation in the use of color additives was soon recognized as a threat to the pubHc s health. Of particular concern were the practices of a dding poisonous colorants to food, and of using dyes to hide poor quaUty or to add weight or bulk to certain items. References 5—14 provide additional information on the history of food colorants and thek regulation. Reference 15 provides more information regarding the appHcations, properties, specifications, and analysis of color additives, as well as methods for the determination of colorants in products. 

Use Restrictions. There are numerous restrictions on the use of color additives. They caimot, for example, be employed to deceive the pubHc by adding weight or bulk to a product or by hiding quaUty. In addition, special permission is needed to use colorants or products containing them in the area of the eyes, in injections, in surgical sutures, and in foods for which standards of identity have been promulgated under Section 401 of the Eederal Eood, Dmg, and Cosmetic Act. 

The use of color graphics is also an effective means for displaying chemical stmctures. This method is far better than typesetting the three-dimensional architecture of complex multimolecule assembly (112). For developing in-house CAD software programs, the three-dimensional, sohd-modeling capabiUties of SdverScreen can also be utilized either in monochrome or color for constmction of such stmctures (113). 

It is desirable for the record to have an objective statement of the nature and degree of color deterioration. The simplest, but least desirable, method is comparison of sample color with color charts or plates such as those used in the Munsell system, Ridgeway s color standards, or the Maerz and Paul dictionary of color. Such a method is limited in value because of the difficulty of obtaining true color matches, and because of variations due to human error. The use of color charts or plates may be much improved in the Munsell system by employing a disk colorimeter (29). Kramer and Smith (21) have pointed out that the results obtained in its application to foods are sometimes difficult to explain and compare, and that the method requires special training of the operator and is tedious and cumbersome. 

In the EU, the use of color additives in food was settled by two directives 94/36/EC, which establishes the list of permitted colors, and 95/45/EC, which deals with purity criteria for colors. Directive 94/36/EC also contains five annexes ... 

Apocarotenoids also act as chemoattractants, repellants, and growth effectors in plants and cyanobacteria. They attract pollinators to plants through the use of color similar to full-length carotenoids. Their aromas are thought to be attractants for animals and insects to facilitate in seed dispersal and pollination. Small volatile apocarotenoids lure pollinators and levels of apocarotenoids... 

The most important UV/VIS applications have been in the fields of color measurement and color matching, areas of great importance to the dye, paint, paper, textile, and printing industries. The pharmaceutical industry has similar interests in that the use of coloring agents in formulations requires specification. Reflectance spectroscopy has been used, however, by a number of workers to study the kinetics and mechanisms associated with a variety of reactions that were found to take place in the solid state. 

Council of Europe Resolution AP (89)1 on the use of colorants in plastic materials coming into contact with food, Sept.19,1990. 

The appreciation of color and the use of colorants dates back to antiquity. The art of making colored candy is shown in paintings in Egyptian tombs as far back as 1500 bc. Pliny the Elder described the use of artificial colorants in wine in 1500 bc. Spices and condiments were colored at least 500 years ago. The use of colorants in cosmetics is better documented than colorants in foods. Archaeologists have pointed out that Egyptian women used green copper ores as eye shadow as early as 5000 bc. Henna was used to redden hair and feet, carmine to redden lips, faces were colored yellow with saffron and kohl, an arsenic compound, was used to darken eyebrows. More recently, in Britain, in the twelfth century, sugar was colored red with kermes and madder and purple with Tyrian purple. 

As this would require time, Wiley arranged for color policy to be deferred from the initial regulations that were to be issued before the act became effective on January 1. When the Department of Agriculture issued the regulations in October, it noted simply that "the Secretary of Agriculture shall determine from time to time. . . the principles which shall guide the use of colors" (4). Neither Wiley nor any of his staff was familiar with these dyes, so in mid summer he hired an outside consultant, Dr. Bernhard C. Hesse of New York City, to study the question. Hesse agreed to devote twenty hours a week to this project (5). 

The use of color-differentiation is favored whereas the use of color coding is controversial because of the limited number of colors, the prevalence of color blindness in the general population, and inappropriate reliance on color in lieu of reading the label. 

Reciprocity failure of the film has two practical implications. The first is seen with the use of color-reversal film. Each of the three color-sensitive layers of the film has a different reciprocity failure factor resulting in incorrect color reproduction during long exposures. To correct for this problem, color-compensating filters can be placed in the light path to the camera. 

The main drawback of the use of color reactions for the analysis of explosives lies in their often low specificity. Although their specificity varies according to the type of reactions - and some reactions are quite specific - it is generally not safe enough to establish an identification of an explosive in a forensic laboratory on color reactions alone. When the color is obtained, the key question is whether other compounds, which are not explosives, can produce the same color under identical experimental conditions. Unfortunately, the answer is usually, yes. Thus, in forensic analysis, where an erroneous identification may lead to a gross injustice, it is generally accepted that the identification of an explosive should not depend on color reactions alone. 

Nagano,T Nakashima, S. Nakayama, S. Se-noo, M. (1994) The use of color to quantify the effects of pH and temperature on the crystallization kinetics of goefhite under highly alkaline conditions. Clays Clay Min. 42 226-234... 

The use of color film for high-speed photographic studies of explosions underwater has been made more feasible by GAF s new Blue-Insensitive Anscochrome Aerial Film which does not have a blue-sensitive top layer (Ref 21). 

Lacquers or varnishes Many metallic cases and components in contact with explosives are protected by coating of lacquers or varnishes. Some varnishes, even after complete curing, have been found to give high gas rates especially with RDX/TNT. Similarly, the compatibility of lacquers is considerably affected by the use of coloring dyes such as rhodamine red dye. 

North American archaeological sites reflect the use of colorants, exemplified by the abundance of die inorganic mineral pigment red ochre in domestic and mortuary contexts in sites from the Clovis through the Mississippian periods (10000 B.P.-1400 A.D.). Typically the presence of these accumulations of pigment minerals is interpreted as material used in ceramics, or for body painting. Color on textiles is not usually considered. 

The use of color by prehistoric peoples was also addressed in Willoughby s discussion of textiles found at the Mississippian temple mound sites of Etowah, Georgia and Spiro, Oklahoma (colored textiles. Kuttruff proposed that the complexity of these textiles including the colored patterning and design motifs is indicative of sophisticated artisanship and status differences that were expressed through clothing (73), but her study did not involve the identification of colorant types. Saltzman (14) identified madder as the dye plant that had been used to color some of the Spiro textiles. 

The TCA cycle. In each turn of the cycle, acetyl-CoA from the glycolytic pathway or from /3 oxidation of fatty acids enters and two fully oxidized carbon atoms leave (as C02). ATP is generated at one point in the cycle, and coenzyme molecules are reduced. The two C02 molecules lost in each cycle originate from the oxaloacetate of the previous cycle rather than from incoming acetyl from acetyl-CoA. This point is emphasized by the use of color. 

Cyclic ethers, cyclic acetals, and some vinyl compounds can be polymerized by cationic processes. Photoinitiation of these polymerizations by ultraviolet light are known (12,106). Some extension of direct photolytic sensitization of cationic processes to visible wavelengths is obtained by the use of colored diazonium salts as initiators. For example, Schlesinger (11a) used diazonium salts substituted in the para position with electron withdrawing groups, but sensitivity was limited to the blue to green regions of the spectrum. 

Optical sensors for ions use indicators, which exist in two different colors, depending on whether the analyte is bound to them. The use of colored indicators is one of the oldest principles of analytical chemistry, used extensively both in direct analytical spectroscopy and in so-called visual titrations. In their sensing application, the indicator is confined to the surface of the optical sensor or immobilized in the selective layer. In that sense, the oldest and most widespread optical sensor is a pH indicator paper, the litmus paper, which is commonly used for the rapid and convenient semiquantitative estimate of pH of solutions or for endpoint detection in acidobasic titrations. Its hi-tech counterpart is a pH optrode (the name of which is intentionally reminiscent of the pH electrode), which essentially does the same thing (Wolfbeis, 2004). The operation principles and limitations of ion optical sensors are common for all ions. 

In the study of chemistry, the atom is the basic structure of matter and protons, electrons, and neutrons are basic subatomic particles. In the study of art, design is the basis of an artistic arrangement, and color is one element of design. The design of a work of art includes not only color but also line, texture, light and dark contrast, and shape. However, color is the element of design that arouses the most appreciation and is the element to which we are most sensitive. Even one who is puzzled by modem art usually finds its color exciting and attractive. One may question the use of distortion of shape but will seldom object to the use of color and may like a work of art solely for its use of color. 

Legislation covers all chemicals, including dyes. Only the use of chemicals and colorants in foodstuffs, food-packaging materials, or pharmaceuticals is mentioned here. The exposure level of dyes is generally very low, but people are inadvertently exposed to dyes and other synthetic chemicals for these applications through dermal contact. Therefore, the use of colorants is especially regulated in many countries. General requirements on dyes for the incorporation into packa-... 

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