Viscosity decoloration

In the glass (qv) and ceramic industry (see Ceramics), barite can be used both as a flux, to promote melting at a lower temperature or to increase the production rate, and as an additive to increase the refractive index of glass. The viscosity of barite-containing glass often needs to be raised. Alumina in the form of feldspar is sometimes used. To offset any color produced by iron from the barite addition, more decolorizer may be needed. When properly used, barytes help reduce seed, increase toughness and brilliancy, and reduce annealing time. Barite is also a raw material for the manufacture of other barium chemicals. 

Mixing time 6 necessary to achieve a molecular homogeneity of a liquid mixture—normally measured by decolorization methods in material systems without differences in density and viscosity depends on only four parameters, stirrer diameter d, density p, dynamic viscosity / , and rotational speed k ... 

In a polar polymer, i.e., cellulose acetate (CA) or nitrocellulose (NC) 35E, 35Z, and 36 had a relatively longer absorption maximum wavelength than in less polar matrices. In NC the of 36 shifts to 528 nm, which is also longer than in organic solvents. The role of polymer films in the quantum yields of photoreactions is not clear. In a comparison of the photochemical properties of 35 in polymer films and in solvents, it was found that the E c in polymer matrices was substantially smaller than that in the corresponding solvent with similar polarity. However, the decoloration quantum yield Oc e in a polymer film was larger than that in solvents. In conclusion, the polymer matrix properties, such as polarity, viscosity, and glass transition temperature (Tg) are quite important for photochromic reactions and applications. The coloration, E — Z and Z —> E isomerizations were suppressed in polymer matrices. 

Aqueous solutions of arabinogalactans are often colored, probably because of the presence of phenolic impurities. Attempts have been made to decolorize such solutions by using active carbon. The viscosity, surface tension, and other solution properties were also investigated. Attempts to use an arabinogalactan as a plasma substitute have not been successful. ... 

It is possible to decolorize by adsorption techniques using materials like the activated carbons, or combinations of the carbons and clays, but only in relatively dilute solutions where the viscosity of the gum arabic will not interfere with the adsorption of color. With most adsorbants, when the gum arabic is dilute enough so that the color is adsorbed, some of the gum arabic is also adsorbed. There is then the problem of concentration without processing the gum arabic at such a temperature that some of the color is restored. The gum can be bleached or decolorized in dilute solution, but then the concentrate must be boiled the concentration, other than at very low vacuum, of the colloidal solutions is a problem without the intooduc-tion of further amounts of color, particularly on surfaces of tubes or in thin films. An attempt is made to get the darker colored materials out by visual selection at an early stage. If it is processed in dilute solution, color comes back when it is concentrated. 

It is -interesting to observe here that less clear-cut separation in slow and fast isomers can occur in the kinetic scheme of the decoloration process. If the rate of decoloration depends to a considerable degree on the viscosity of the polymer matrix, it is also a very well known fact that the distribution of free volume in the glassy state can be Inhomogeneous, giving rise to a broad spectrum of relaxation times. This leads to a more complex mechanism of one-step chemical reactions in glassy polymers (111-114). 

In general, the hydrocarbons are adsorbed in the following order unsaturates, aromatics, naphthenes, and paraffins. In each series the high-molecular-weight hydrocarbons are adsorbed more readily, and this doubtless accounts for most of the decolorizing action. Thus the specific gravity, viscosity, and color of the stream of oil from a percolation filter increase as more and more oil flows through the filter, and the first oil... 

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