Visual color, problems

The indirect methods discussed thus far have dealt with measurement of color only as it can be correlated with physical characteristics of materials and the effect of these materials on radiant energy. As has been pointed out, the reflectance spectro-photometric curve describes a property of the material. A change in the reflectance spectrophotometric properties may not always result in a change in visual color. The reason is that color of the object is not an unchangeable characteristic of the object itself, dependent only upon these reflectance properties, but is also dependent upon the quality of the illuminating light and the sensitivity of the observer s eye. Thus the measurement and description of visual color are psychophysical problems... 

The best method for evaluation of the color problem is to prepare a food product containing the protein flour. Biscuits were routinely used as the model food system. Figure 5 illustrates the color of biscuits prepared with lOOZ wheat flour and with 20Z plant-protein products. The color of the biscuits prepared with soybean and peanut flours shows that these ingredients do not cause a serious color problem. However, sunflower, alfalfa leaf, and cottonseed flours do produce a discoloration in this model food system. The L and b values generally reflect this visual evaluation. 

The character of AR/TS is changing. Materials, equipment and applications are all increasingly sophisticated. There is more need for expert personnel, yet flexibility and breadth of outlook are required to cope with new situations. How does one predict the weatherability of plastics when twenty years service is the objective The organizers of a 1967 symposium on the subject felt obliged to conclude that after a century the problem is still far from a satisfactory solution (9). How does one predict with reliability the hazard to a large population of a new food additive or soap bacteriostat over a long period of time How does one deal with subjective properties of chemicals such as taste and flavor The synthetic sweeteners in use today have all been discovered accidentally is this the way to run a chemical business How are reluctant old timers weaned from visual color matching to computers ... 

AE (CIELab) is a widely used measure of color difference. However, because AE (CIELab) is derived from a rectangular coordinate system, and visual color perception is elliptical in nature, it was recognized that there were areas in which the setting of tolerances for visual color difference were unacceptable. CIELCh color space, a cylindrical coordinate system, addresses some of these problems and gives better correlation with the elliptical response of the eye. Further enhancement of this correlation has been made using the CMC tolerancing modification to CIELCh to obtain AE (CMC). CMC refers to the Color Measurement Committee of the Society of Dyers and Colourists. As an introduction to color difference, color tolerancing, and other aspects of color measurement, some of the publications available from spectrophotometer manufacturers are quite helpful. Additional information on color difference can be found in any of the color measurement references cited, particularly. Refs. 6-8 and 14. 

This is a qualitative problem requiring you to visualize and represent molecules, hi molecular pictures, circles represent atoms, and different colors or shadings identify different elements. The problem does not state how many atoms and molecules to draw, so we can start with any convenient amounts. However, the numbers of atoms of each element must not change during the reaction. 

This problem can be partly overcome by using several weights simultaneously to create the display. A visually appealing way to do this is to choose the same group of three weights at each node and interpret them as RGB (red, green, blue) values, then to plot on the map a blob of the appropriate color at the position of the node. 

The perception of color is subjectively developed in the mind of an individual, and consequently different people can perceive a given color in various ways. Such variability in interpretation causes great difficulty in the evaluation of color-related phenomena, leading to problems in making objective judgements. The development of quantitative methods for color determination was undertaken to eliminate the subjectivity associated with visual interpretative measurements. 

Table 1 can be used as a guide to define hazardous wastes from textile plants. Besides the direct toxicity of substances like chlorinated hydrocarbons, organo-Hg compounds, or concentrated alkaline solutions, other parameters have been defined with regard to problems during biodegradation or accumulation in the sludge from CWWT. A particular situation is found with colored effluents, where limits for spectral absorption have been defined. While the toxicity of textile dyes is comparably low, these limits were derived from the visual aspect of the water released from a textile plant because they look unhealthy. ... 

A colorimetric method based on the violet color produced by ferrous sulfate in sulfuric acid in the presence of N03 was announced by English in 1947 (Ref 9) and applied to the determination of NA and nltrosylsulfuric acid (NSA) in spent mixed acid. Since then a number of papers (Refs 13, 14, 15, 16 and 17) have extended the method to NOa, organic nitrates and RDX -HMX mixtures Analytical Methods The visual determination of the endpoint (appearance of a permanent brown color) in the dead-stop titrimetric method is reported accurate to 0.03ml (Ref 3) and was used recently by Frejacques and LeClercq (Ref 12) for analysis of Pentolites, Tetryls, NGu, NG prepns, and Nitroethane-EGDN expls. The endpoint has been criticized as difficult to see, and if problems arise, electrometric methods are available for detection (Refs 6,... 

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