Chroma

Gr. chroma, color) Discovered in 1797 by Vauquelin, who prepared the metal the next year, chromium is a steel-gray, lustrous, hard metal that takes a high polish. 

Electromagnetic unit emu Flow rate, column chroma- Fo... 

LC can be used for both volatile and nonvolatile substances, but GC can handle only volatile substances. Chromatography was originally a method for separating and displaying mixtures of colored substances on a colorless column of solid material. The word chromatography is derived from chroma (color) and graph (writing). 

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. 

In general, all iron pigments are characteri2ed by low chroma and excellent Hghtfastness. They are nontoxic, nonbleeding, and inexpensive. They do not react with weak acids and alkaHes, and if they are not contaminated with manganese, do not react with organic solvents. However, properties vary from one oxide to another. 

Chromium was first isolated and identified as a metal in 1789 by Vauquelin who was working with a rare mineral, Siberian red lead or crocoite [14654-05-08] PbCrO (3). The name chromium comes from the Greek word chroma color and resulted from the wide variety of brilliant colors... 

The close analogy of to the MunseU hue and of to the MunseU chroma of Figure 4 is evident LY is also closely related to the MunseU value. 

Iron Oxides. In addition to the black iron oxide, there are several natural and synthetic yellow, brown, and red oxides. As a class, they provide inexpensive but dull, lightfast, chemically resistant, and nontoxic colors. The natural products ate known as ocher, sieima, umber, hematite, and limonite. These include varying amounts of several impurities in particular, the umbers contain manganese. Their use is limited because of low chroma, low tinting strength, and poor gloss retention. 

Kany, E., Jork, H. GDCh-training course Nr. 300 Einfiihrung in die Diinnschicht-Chroma-tographie , Saarbrileken 1986. 

The high thermal and chemical stability of fluorocarbons, combined with their very weak intermolecular interactions, makes them ideal stationary phases for the separation of a wide variety of organic compounds, including both hydrocarbons and fluorine-containing molecules Fluonnated stationary phases include per-fluoroalkanes, fluorocarbon surfactants, poly(chlorotrifluoroethylene), polyfper-fluoroalkyl) ethers, and other functionalized perfluoro compounds The applications of fluonnated compounds as stationary phases in gas-liquid chroma... 

Unfortunately, most column and sorbent manufacturers do not develop column packing materials mainly for SEC work, but for the bigger high-performance liquid chromatography (HPEC) market. However, there are many important differences to consider when designing packings for different modes of chroma-... 

Finally, in 1797, the Frenchman L. N. Vauquelin discovered the oxide of a new element in a Siberian mineral, now known as crocoite (PbCr04), and in the following year isolated the metal itself by charcoal reduction. This was subsequently named chromium (Greek xpco ia, chroma, colour) because of the variety of colours found in its compounds. Since their discoveries the metals and their compounds have become vitally important in many industries and, as one of the biologically active transition elements, molybdenum has been the subject of a great deal of attention in recent years, especially in the field of nitrogen fixation (p. 1035). 

Methods are described for determining the extent to which original natural color is preserved in processing and subsequent storage of foods. Color differences may be evaluated indirectly in terms of some physical characteristic of the sample or extracted fraction thereof that is largely responsible for the color characteristics. For evaluation more directly in terms of what the observer actually sees, color differences are measured by reflectance spectrophotometry and photoelectric colorimetry and expressed as differences in psychophysical indexes such as luminous reflectance and chromaticity. The reflectance spectro-photometric method provides time-constant records in research investigation on foods, while photoelectric colorimeters and reflectometers may prove useful in industrial color applications. Psychophysical notation may be converted by standard methods to the colorimetrically more descriptive terms of Munsell hue, value, and chroma. Here color charts are useful for a direct evaluation of results. 

Conversion tables and charts now available make it possible to express I.C.I. data in forms in which a specified color and the significance of measured color differences can be more easily visualized. For example, I.C.I. values calculated from objective instrumental readings can be converted into the Munsell notation which evaluates the three psychological color attributes—hue, lightness (Munsell value), saturation (Munsell chroma)—on scales of approximately equal visual steps. In addition, the Munsell color charts offer one of the most convenient sources of material standards for direct color comparisons. 

Chromatin is a noncovalent complex consisting of DNA and dedicated packing proteins, the histones. The name chromatin is derived from the Greek word chroma... 

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