Colorants reducing properties

Other Borohydrides. Potassium borohydride was formerly used in color reversal development of photographic film and was preferred over sodium borohydride because of its much lower hygroscopicity. Because other borohydrides are made from sodium borohydride, they are correspondingly more expensive. Generally their reducing properties are not sufficiently different to warrant the added cost. Zinc borohydride [17611-70-0] Zn(BH 2> however, has found many appHcations in stereoselective reductions. It is less basic than NaBH, but is not commercially available owing to poor thermal stabihty. It is usually prepared on site in an ether solvent. Zinc borohydride was initially appHed to stereoselective ketone reductions, especially in prostaglandin syntheses (36), and later to aldehydes, acid haHdes, and esters (37). 

In 1864, W Weyl also observed the blue color of alkali metals solutions in ammonia, methylamine and ethyl amine and found that the resulting solutions had reducing properties, when used in chain synthesis. However, W Weyl did not discover the nature of these blue solutions. Nowadays, it is known that the blue color is due to the solvated electron, as alkali metals dissolved in amine solvents give the metal cation and a solvated electron as in the case of sodium ... 

Greenish-yellow powder, d 3.363. mp approx 1406°. Sublimes at bright red heat. Almost insol in water, alcohol, acetone, ethyl acetate, acetic anhydride, glacial acetic acid, toluene, carbon tetrachloride, chloroform, carbon disulfide. Black color with NaOH soln. Aq solns have strong reducing properties. 

When paper is impregnated with lead acetate, it assumes a dark color when in contact with HjS. This, in turn, changes its reflectance (as measured at 580 nm). Levels as low as 50 ppb of HjS could be measured with high reproducibility [143]. Other methods for sensing H2S are based on the reducing properties of sulfide or hydrogen sulfide [94,96]. These devices are, however, probes rather than sensors because they act irreversibly. 

Non-specific visualization procedures (e.g., charring) for tocopherols/tocotrienols are based on spraying with sulfuric acid, perchloric acid, nitric acid, or copper (II) sulfate phosphoric acid (54). More specific though still subject to many interferences are reactions which take advantage of the reducing properties of vitamin E derivatives. In the Emmerie-Engel reaction and its later modifications, ferric ions are reduced to ferrous ions, which form a red-colored complex with a,a -dipyridine ot bathophenanthroline (50,51). A comparable sensitivity is achieved by spraying with phospho-molybdic acid. The color can be stabilized by subsequent exposure of the plates to ammoniacal 2,7-dichlorofluorescein (51). 

Poly(ethylene terephthalate) (PET) is often used for beverage containers. For such applications, the fabricated PET bottle must exhibit low color and high transparency, and in addition to low taste and odor, the additive must be non-toxic. These requirements impose further important issues for a slip agent in addition to its friction-reducing properties (5). 

Coextrusion is a process that allows for extrusion of two or more materials. Typically, there is a surface layer and a core layer. The core layer often uses a less expensive material and often process regrind material is considered for this appUcation. The surface layer material is chosen to meet the appearance and performance requirements of the part. The surface layer material is usually more expensive because it has the colorants and property enhancement additives to meet the part requirements. With coextrusion process, the thickness of the surface layer is typically minimized to reduce the cost. This has made coextrusion a cost-effective method for mold-in-color parts compared to straight extrusion or coating. The coexftusion process has been successfully used for profile coextruded body-side molding applications. 

Features Compat. with anionic, cationic, nonionic material chemically stable in the pressence of acids, alkalis, oxidizers, reducers Properties Liq. Gardner color 8 max. sol. in ethanol, water, xylene disp. in isopropyl alcohol, propylene glycol, wh. spirit, low aromatic solv. dens. 1045 kg/m vise. 350 mPa S cloud pt, (1% in 10% NaCI) 85 C flash pt (PMCC) > 100 C surface tens. 45 mN/m wetting power > 600 sec, 100%... 

Formation of D-fructo ranosyl carboxonium (oxycarbenium) ions by reaction of free sucrose-OH-groups to a mixture of 41% oligosaccharides and 46% polysaccharides with hydrophilic, waterabsorbing properties with added alcohols, they produce glycosides, the properties of which are determined by the nature of the alcohols Possible drawbacks in these chemical modifications may arise from the tendency of inversion, which leads to reducing properties, acidic or alkaline degradation and color formation, depending on the environmental conditions of the reaction. 

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