Value, colorant properties

Properties of Colorants. Properties of a number of colorants are shown ia Tables 5—9. Eor other properties see Refereace 15. Most values are from the Hterature and, ia geaeral, refer to commercial colorants and not pure compounds. The composition of certified colorants can vary substantially with regard to the amounts of pure dye, salt, moisture, subsidiary dyes, trace metals, etc. that they contain, and of course the properties of color additives are affected by their composition. 

Mie s Theory. Mie applied the Maxwell equations to a model in which a plane wave front meets an optically isotropic sphere with refractive index n and absorption index k [1.26]. Integration gives the values of the absorption cross section QA and the scattering cross section Qs these dimensionless numbers relate the proportion of absorption and scattering to the geometric diameter of the particle. The theory has provided useful insights into the effect of particle size on the color properties of pigments. 

Color Strength, Hue, Chroma [20, p. 99-105], The coloring properties of a dye are assessed by preparing a dyed test sample whose color is evaluated. This must, in principle, always be done by the human eye because color perception, being a subjective sense impression, is not accessible to direct measurement. However, with the aid of colorimetry this visual perception can be represented more or less closely by measurable quantities. Since colorimetry is an objective method and is therefore more accurate and reproducible than subjective visual assessment, it is veiy widely used today. Color is a three-dimensional quantity and must therefore be expressed by a set of three numbers (color coordinates). In practice, these are typically the values of color strength, hue, and chroma. 

The above relationships (Figure 1.10) show that the optical pigment properties depend on the particle size D and the complex refractive index n = n (1 - i/c), which incorporates the real refractive index n and the absorption index k. As a result, the reflectance spectrum, and hence the color properties, of a pigment can be calculated if its complex refractive index, concentration, and particle size distribution are known [1.40]. Unfortunately, reliable values for the necessary optical constants (refractive index n and absorption index k) are often lacking. These two parameters generally... 

The temperature factor (together with the Cartesian coordinates) is the result of the rcfincincnt procedure as specified by the REMARK 3 record. High values of the temperature factor suggest cither disorder (the corresponding atom occupied different positions in different molecules in the crystal) or thermal motion (vibration). Many visualisation programs (e.g., RasMol [134] and Chime [155]) have a special color scheme designated to show this property. 

To display properties on molecular surfaces, two different approaches are applied. One method assigns color codes to each grid point of the surface. The grid points are connected to lines chicken-wire) or to surfaces (solid sphere) and then the color values are interpolated onto a color gradient [200]. The second method projects colored textures onto the surface [202, 203] and is mostly used to display such properties as electrostatic potentials, polarizability, hydrophobidty, and spin density. 

Color and Coloring Materials. The third key property of all types of ink is color which may very weU be the most important one to the consumer because it has such a great psychological impact. Color (qv) has three different attributes described as hue or shade, saturation or chroma, and lightness or value. 

The value of pigments results from their physical—optical properties. These ate primarily deterrniaed by the pigments physical characteristics (crystal stmcture, particle size and distribution, particle shape, agglomeration, etc) and chemical properties (chemical composition, purity, stabiUty, etc). The two most important physical—optical assets of pigments are the abiUty to color the environment in which they ate dispersed and to make it opaque. 

The properties of textile fibers can be divided into three categories geometric, physical, and chemical, which can be measured with available methods (15—17). Perceived values such as tactile aesthetics, style appearance of apparel fabrics, comfort of hosiery, as weU as color, luster, and plushness of carpets are difficult to quantify and are not always associated with the properties of the fiber, but rather with the method of fabric constmction and finishing. 

Fmctose is a highly reactive molecule. When stored in solution at high temperatures, fmctose not only browns rapidly but also polymeri2es to dianhydrides [38837-99-9] [50692-21-2] [50692-22-3] [50692-23-4] [50692-24-5]. Fmctose also reacts rapidly with amines and proteins in the nonen2ymatic or MaiUard browning reaction (5). This is a valued attribute in baked food products where cmst color is important. An appreciation of these properties allows the judicious choice of conditions under which fmctose can be used successfully in food appHcations. 

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