Color density definition

The term electrochromism was apparently coined to describe absorption line shifts induced in dyes by strong electric fields (1). This definition of electrocbromism does not, however, fit within the modem sense of the word. Electrochromism is a reversible and visible change in transmittance and/or reflectance that is associated with an electrochemicaHy induced oxidation—reduction reaction. This optical change is effected by a small electric current at low d-c potential. The potential is usually on the order of 1 V, and the electrochromic material sometimes exhibits good open-circuit memory. Unlike the well-known electrolytic coloration in alkaU haUde crystals, the electrochromic optical density change is often appreciable at ordinary temperatures. 

The bronze solutions have the following characteristics (i) a bronze color with a definite metallic luster (2) very low densities (3) conductivities in the range of metals and (4) magnetic susceptibilities similar to those of pure metals. All of these properties are consistent with a model describing the solution as a dilute metai or an alloy in which the electrons behave essentially as in a metal, but the metal atoms have been moved apart (compared with the pure metal) by interspersed molecules of ammonia. 

When petroleum occurs in a reservoir that allows the crude material to be recovered by pumping operations as a free-flowing dark to light colored liquid, it is often referred to as conventional petroleum. Heavy oils are the other types of petroleum that are different from conventional petroleum insofar as they are much more difficult to recover from the subsurface reservoir. The definition of heavy oils is usually based on the API gravity or viscosity, and the definition is quite arbitrary although there have been attempts to rationalize the definition based upon viscosity, API gravity, and density. 

It is customary to say that under the same external conditions all specimens of a particular substance have the same specific physical properties (density, hardness, color melting point, crystalline form, etc.). Sometimes, however, the word substance is used in referring to a material without regard to its state of aggregation for example, ice, liquid water, and water vapor may be referred to as the same substance. Moreover, a specimen containing crystals of rock salt and crystals of table salt may be called a mixture, even though the specimen may consist entirely of the one chemical substance sodium chloride. This lack of definiteness in usage seems to cause no confusion in practice. 

This property was recognized in ancient times (remember the story of Archimedes who was almost arrested for public indecency) as an excellent indicator of the identity of a pure substance, regardless of color, texture, etc. You can see from the definition that the density must vary as temperature is changed. The volumes of liquids increase as the temperature increases, and therefore the density of liquids must decrease as the temperature increases. The density, as defined, provides us with a useful conversion factor for the conversion of grams to milliliters or milliliters to grams. 

It is noteworthy that once the state of a substance is fixed by conditions 1-6, all physical properties (except for the form of a solid), including viscosity, thermal eonduetivity, color, refractive index, and density, take on definite values. Furthermore, the state of a substance is independent of its position in a gravitational field and its velocity. Although there are other conditions (magnetic field strength, surface area) whose values are needed under certain conditions, the six conditions listed above are usually sufficient to fix the state of a substance. 

In this same model we find that both the r and r density distributions give a silicate residual intensity only 30% of the neighboring continuum. The observed ratio is 25% (Gillett and Forrest 1973). Two quite definite predictions of this interpretation of the silicate feature as compared with extrinsic absorption models are that there should be a strong correlation between sources with low color temperature and deep silicate absorption and sec-condly there should be little or no 20y absorption (also from silicates) for sources with color temperature greater than 200°K if the 10]i feature is intrinsic ... 

Figure 3 In the upper part the particles density p vs position y — jcms citid time X is shown for three dijferent velocities (a),(h) v = 0.02, (c) v = 0.04, and (d) v — 0.4, respectively. The white and black colors indicate low and high density, respectively [ the gray scales are chosen independently for each suhfigure to maximise contrast]. The definition of the shearon wave vector q is examplified in (a) and (b), where the arrows indicate / 2q ) and j 2q2), respectively. In the lower part the resulting normal motion of the top plate Y is represented. The model parameters are ay = 1, = 0.5,...

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