Dark-colored components

Figure IB shows the effect of HLB value of the two Tween (TW) series surfactants on digestibility using a surfactant loading of 0.5 wt%. The HLB values of TW-85 and TW-80 are 11.0 and 15.0, respectively (Table 1). Unlike NP series surfactants, the dark-colored components were not distributed among the fibers (not shown). However, a slightly thicker band than the one formed in the control sample was observed in the upper portion of the bottle. As in NP series surfactant, digestibility did not depend on the HLB value. From the results shown in Fig. 1, it can be said that surfactants can improve ink removal efficiency, but not enzymatic digestibility.

Saussure (1804) is usually credited with introducing the term humus (Latin equivalent of soil) to describe the dark-colored organic matter in soil. Somewhat later, Dobereiner (1822) designated the dark-colored component of soil organic matter as Humussdure or humus acid. The origin of the term humic acid to identify the alkali-soluble, acid-insoluble fraction is somewhat obscure but it was in common use by the time of Berzelius (1839). Waksman (1936) pointed out that humus acid and humic acid were often used indiscriminately and seldom was any differentiation made between the two when distinguished, the former referred to the alkali extracted material, whereas the latter referred to the precipitate obtained by acidification. Use of the term humin to describe the alkali-insoluble material had a similar develop-... 

This test method is for detennininghydrocaitMn types over the concentration ranges from S to 99 volume % aromatics, 0.3 to SS volume % olefins, and 1 to 9S volume % saturates in petroleum fiactions that distill below 31S C. This test method may apply to concentrations outside these ranges, but the precision has not been determined. Samples containing dark-colored components that interfere in reading the chromatographic bands cannot be analyzed. 

Properties. Uranium metal is a dense, bright silvery, ductile, and malleable metal. Uranium is highly electropositive, resembling magnesium, and tarnishes rapidly on exposure to air. Even a poHshed surface becomes coated with a dark-colored oxide layer in a short time upon exposure to air. At elevated temperatures, uranium metal reacts with most common metals and refractories. Finely divided uranium reacts, even at room temperature, with all components of the atmosphere except the noble gases. The silvery luster of freshly cleaned uranium metal is rapidly converted first to a golden yellow, and then to a black oxide—nitride film within three to four days. Powdered uranium is usually pyrophoric, an important safety consideration in the machining of uranium parts. The corrosion characteristics of uranium have been discussed in detail (28). 

Spent foundry green sand is of particular interest to soil blending companies that produce topsoil, because of its dark color, clay content, moisture retention, and consistency. A high sand content is required in topsoil, so spent foundry sand could be a major component. Spent sand reduces the... 

Under saturated or very wet conditions, soils tend to have increased amounts of OM. This results in dark colors and dramatically changes the chemical characteristics of a soil. OM increases a soil s sorptive and cation exchange capacities and thus alters the movement and extraction of components present. OM increases ped formation and stability, thus increasing both aeration and percolation, but under saturated conditions, reduction reactions prevail (see Figure 2.12). 

Implementation The IR spectrum is obtained as a smear on salt crystals. Not surprisingly, the spectrum shows soap and triglyceride, but is of poor quality and not suitable for identification of the other components. The dark color of the sample may indicate charring and is likely partly responsible for the quality of the spectrum. 

The term varnish is used to describe the hard, amber-colored coating of fuel oxidation products adhering to engine components. The term sludge is used to describe the heavy, dark-colored deposits which settle from solution out of the fuel. Sludge can accumulate in areas of low turbulence and act as a prime site for initiating corrosion. 

Vauquelin (14), A. Klaproth (6), and R. Jameson (5), alkali soluble organic constituents of soil and coal are designated as humic acids/ Collectively, these substances make up an ill-defined series of dark colored, weakly acidic solids which form whenever plant components (such as lignin) are exposed to fungal oxidases, or when coal is allowed to weather or otherwise oxidize. Some evidence now exists that humic acids isolated from these varied sources do indeed contain several common peripheral structures (2, II, 16), but by any more discriminating test, the term possesses little chemical significance or fixed meaning. 

Plasticizers. These materials are added to reduce the hardness of the compound and can reduce the viscosity of the uncured compound to facilitate processes such as mixing and extruding. The most common materials are petroleum-based oils, esters, and fatty acids. Critical properties of these materials are their compatibility with the rubber and their viscosity. Failure to obtain sufficient compatibility will cause the plasticizer to diffuse out of the compound. The oils are classified as aromatic, naphthenic, or paraffinic according to their components. Aromatic oils will be more compatible with styrene-butadiene rubber than paraffinic oils, whereas the inverse will be true for butyl rubber. The aromatic oils are dark colored and thus cannot be used where color is critical, as in the white sidewall of a tire. The naphthenic and paraffinic oils can be colorless and are referred to as nonstaining. 

Asphaltene is an essential component of any dark-colored, heavy, viscous and nonvolatile oil, regardless of the oil source. Asphaltene can be obtained from the oil extracted from a naturally occurring organic-rich fossil material by a simple solvent fractionation. Asphaltene also can be obtained from the chemical conversion product of a solid fuel, such as pyrolysis or catalytic hydrogenation of coal or shale. The former is an example of the asphaltene isolated from native petroleum oil. An example of the latter is the asphaltene obtained from a synthetic crude, such as shale oil or coal liquid. 

If precipitation lines contain a lipoid component, they can be stained with a combination of oil red and Sudan black (Ul), first using a solution of 1 g of oil red O or scarlet red R (Geigy) or Sudan IV dissolved in one liter of 60 % ethanol during 24 hours at 37 °G. The solution is filtered after cooling and kept in dark-colored bottles. The agar films remain 16 hours in this solution then they are soaked for 2 hours in a... 

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