Colors, complementary

Mixed indicators For certain titrations, particularly those carried to a definite end-point pH value, sharpening of the color of an indicator is desirable. This can be accomplished by either of two methods addition of a pH-insensitive dye that produces a color complementary to one of the indicator colors, or use of two indicators of closely adjoining pA, values so that the overlapping colors are complementary at an intermediate pH value. " ... 

Wavelength Range (nm) Wave Numbers (cm ) Color Complementary Color... 

The iodine solution was markedly discolored where it had been hit by the yeUow ray and, when carefully replaced in front of the refracted light, fully bleached in that part after a further hour exposure. Thus, the color complementary of that of the solutions was both absorbed and chemically active, or as Grotthuss put it, light of a color tended to destroy the body that has a color contrary to its own and to cmiserve that that has the same or a similar one. This observation was occasirmally verified by other scientists [8]. 

A color wheel such as the one shown below can be used to approximate the relationship between observed and absorbed colors. Complementary colors are shown on opposite sides of the color wheel. So if a substance absorbs red light, it will be observed to be green. The color wheel will be useful in answering problems 4.60,4.61, and 4.62 on the next page. 

In general terms, a colored filter attenuates the influence of the color complementary to it, and favors the spectral band corresponding to its own color. 

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