Color physical nature

Some of the properties of solutions depend on the chemical and physical nature of the individual solute. The blue color of a copper(II) sulfate solution and the sweetness of a sucrose... 

Just as with organic combustion aerosols, the chemical and physical nature of inorganic solid substrates can have a dramatic impact on the photoreactivity of adsorbed PAH. In 1980, Korfmacher and co-workers reported that BaP, pyrene, and anthracene all pho-tolyzed efficiently in liquid solution but were resistant to photodegradation when adsorbed on coal fly ash. Subsequent studies confirmed this observation and revealed that the carbon content of the ash (and the associated darkening of color) is a key factor in establishing the photostability of these PAHs. Indeed, they were stabilized at relatively small percentages of carbon, e.g., 5% or less (Behymer and Hites, 1985, 1988 Yokley et al., 1986 Dunstan et al., 1989 Miller et al., 1990). 

The structural and chemical causes of color in natural materials can be very complex. But basically, visible colors are caused and affected by the amount of a pigment or impurities present in a material, or the physical structure of its surface. Color is consistent for some materials, and not for others. This depends on the causes of the color. 

The nature of the union between a dye and a fabric is still an open question. It is probable that in certain cases chemical compounds are formed, and that in others the fabric forms with the dye a solid solution, or holds it mechanically within its fibers as the result of adsorbtion. The fact that many colored substances which contain weakly acidic or basic groups dye wool and silk but do not dye cotton is evidence that the fixing of the dye in the animal fiber is probably the result of chemical action. Wool and silk are proteins and cotton is a carbohydrate. The proteins form compounds with weak acids and bases, whereas cotton, which is cellulose reacts only with the strongest acids and bases. Cotton can be dyed by some organic compounds, however,—a fact which leads to the view that in certain cases the union of the dye and the fabric is of a physical nature. 

The apparent source materials for forming such a hypothetical humic polymer would be lignin degradation products or plant polyphenols such as flavonoids. Because it has little relationship with the physical or chemical characteristics of actual humic materials, this type of model has fallen out of favor almost completely, except for ambiguous statements, still occasionally encountered, that the color of natural waters is due to tannins. ... 

For the visual assessment of a color, a reference sample is needed. Systems of physical color samples are available for reference purposes, such as the Munsell system, DIN color chart. Natural Color System and the more customized RAL and Pantone color charts. The ISO grey scale is defined for the visual assessment of color differences and used for the specification of color tolerances for quality control purposes. 

In looking back over 26 years of commercial experience It Is appropriate to comment on product quality. Significant improvements have been made compared with the commercial Delrin of 1960 in terms of melt stability, molecular weight distribution and control, the level and uniformity of physical properties and the color and colorability of natural color product. These product improvements were achieved by persistent chemical and engineering effort on the chemistry of the process, modernization of equipment, compounding technology and automated measurement and control systems. 

The physical properties of the fatty acid ethoxylates depend on the nature of the fatty acid and even more on ethylene oxide content. As the latter increases, consistencies of the products change from free-flowing Hquids to slurries to firm waxes (qv). At the same time, odor, which is characteristic of the fatty acid, decreases in intensity. Odor and color stabiUty are important commercial properties, particularly in textile appHcations. Oleic acid esters, though possessing good functional properties, cannot be used because they tend to yellow on exposure to heat and air. 

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