Synthetic colorants brown

Iron Oxides. In addition to the black iron oxide, there are several natural and synthetic yellow, brown, and red oxides. As a class, they provide inexpensive but dull, lightfast, chemically resistant, and nontoxic colors. The natural products ate known as ocher, sieima, umber, hematite, and limonite. These include varying amounts of several impurities in particular, the umbers contain manganese. Their use is limited because of low chroma, low tinting strength, and poor gloss retention. 

The combined use of a continuous flow system and a spectrophotometer for sample screening to discriminate between synthetic and natural colorants is also available. With a very simple flow system on a column packed with natural materials, one can discriminate natural and synthetic colorants. The natural (not retained) ones can be determined in the first step and the synthetic (retained) ones in the second step after their elution. For yellow, red, green, blue, and brown, natural or synthetic colorants were chosen as models. The specific maximum wavelength for each color (400,530, and 610 mn, respectively) was selected by a diode array system. A complete discrimination of natural and synthetic colorants was obtained for concentrations of natural colorants (in the absence of synthetic ones) up to 2000 (yellow), 2000 (red), and 10,000 (brown) times that of the detection limits (DLs) of synthetic additives. This method was applied to screen fruit drinks and candies. ... 

A systematic study was carried out using in parallel 50 standard solutions for each concentration of three natural colorants (curcumin, carminic acid, and caramel as yellow, red, and brown, respectively). No false positive results for synthetics were obtained up to concentrations of 15 and 20 ng/ml for natural red and yellow colorants, respectively, or 110 ng/ml for natural brown colorant. The concentrations have to be high enough to prove that the screening method is able to accurately discriminate natural and synthetic colorants. To make a clear interpretation of the quantitative UV-Vis spectrum, linear regression analysis was used. Quantitative UV-Vis analysis of a dye ° can be calculated according to the following formula ... 

The use of polyamide is advantageous because it separates natural from synthetic coloring material, removes sugars, acids, and flavoring materials, and concentrates dilute solutions of colors (156,167). However, the use of polyamide is not applicable to chocolate brown FB, chocolate brown HT, or indigotine, because the two chocolate browns are not completely eluted from the column and indigotine decomposes during extraction (157). 

Color. Food color means to a cook what paint means to an artist. Without the bright colors of vegetables and fruits, our meals would be a series of brown and white pictures. Synthetic colors are covered in the section on "Coloring of Food" this section pertains to natural colors. 

As with most nonpolar hydrocarbon-intense polymers, bitumens exhibit good resistance to attack by inorganic salts and weak acids. They are dark, generally brown to black, and their color is difficult to mask with pigments. They are thermoplastic materials with a narrow service temperature range unless modified with fibrous fillers and/or synthetic resins. They are abundant materials that are relatively inexpensive, thus their use in many bulk applications. 

One aspect that limits the use of ILs in optical applications is that many synthetic methodologies lead to yellowish or even brown ILs. Specifically, during fhe preparation of l-alkyl-3-methylimidazolium halides that are frequently used as starting materials in the synthesis of other ILs, discoloration is difficult to avoid. Thus, most commercially available ILs contain colored impurities. Apparently these impurities do not affect organic or catalytic reactions which are carried out in ILs. 

The continually increasing importance of iron oxide pigments is based on their nontoxicity chemical stability wide variety of colors ranging from yellow, orange, red, brown, to black and low price. Natural and synthetic iron oxide pigments consist of well-defined compounds with known crystal structures [3.1] ... 

SDO (Synthetic Drying Oil). A commercial polymer of acetylene (such as SDO-80) which was evaluated as an incendiary mixt component during WWII. A typical mixt contg 1 p of SDO-80 was mixed with 2p of Na nitrate, and the material was exposed to the air with occasional stirring until it had absorbed sufficient oxygen (about 64% of its wt) to form a sticky brown-colored gel. The gel, when ignited, gave a burn time of brief duration and little incendiary value. It was considered to be about 1/10 as effective as a Mg bomb and 1/5 as effective as a gum incendiary mixt of that era. Its performance was comparable to that of thermite Refs 1) L.F. Fieser, OSRD 173 (1941)... 

Mescaline (3,4,5-trimethoxyphenethylamine) (Fig. 5) is mainly contained in Lophophora williamsii peyote, a cactus native to the deserts of Mexico. Peyote contains an average of about 1.5 % of mescaline. It is often synthetic and looks like a clear powder with colors ranging from white to brown, depending on purity. 

Diamonds are the hardest natural substance, but they can cleave easily. They occur in every color, but shades of yellow and brown are most common. Today s faceted diamonds are cut and polished with tools embedded with tiny diamond chips or dust. Before the advent of modern methods, diamonds were used in their natural state, or roughly shaped and polished by hand. The hardness of this mineral led many early jewelers to do a minimum of work before setting diamonds in jewelry or regalia. Common imitations of diamond are colorless spinel, sapphire, zircon, topaz, quartz, and many synthetics. 

Brown, D. (1987) Effects of colorants in the aquatic environment. Chemosphere, 12, 397 104 Cafiizares, P., Dfaz, M., Dominguez, J.A., Garcia-Gdmez, J. and Rodrigo, M.A. (2002) Electrochemical oxidation of aqueous phenol wastes on synthetic diamond thin-film electrodes. Ind. Eng. Chem. Res. 41,4187 1194... 

In addition to its synthetic value, the permanganate oxidation of alkenes provides a simple chemical test for the presence of an alkene. When an alkene is added to a clear, deep purple aqueous solution of potassium permanganate, the solution loses its purple color and becomes the murky, opaque brown color of Mn02. (Although there are other functional groups that decolorize permanganate, few do it as quickly as alkenes.)... 

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