Yellow pigments synthetic iron oxides

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] ... 

Yellow iron oxide n. Fe203-xH20. Pigment yellow (77492). A natural or synthetic iron oxide. It has excellent bleed resistance, chemical resistance (both acid and alkali), lightfastness, and dispersibility, as well as excellent toxicity ratings. However, these yellow oxides have only fair heat resistance since they are subject to color change bout 177°C due to loss of water of hydration. Syn ferrite yellow, ocher, monohydrate of ferric oxide, and limonite. 

The most important coloured inorganic pigments are iron oxides, which provide shades ranging from yellow and red to brown and black. These pigments are manufactured either from natural deposits or by synthetic routes. However, the S3mthetic products, which offer the advantages over their natural counterparts of higher chemical purity and better... 

Synthetic iron oxide pigments are more popular because of their better color purity, consistent properties, and superior tinting strength compared to natimal iron oxide pigments, which is a result of their higher chemical pinity. They are available in red, yellow, brown and black colors. 

Synthetic Yellow Ocher n Synthetic yellow iron oxide reduced with aluminum silicate and other extender pigments. See Iron Oxides, Synthetic. 

Lepidocrocite is found in both natural and synthetic iron oxide pigments. Colour changes with increasing particle size from yellow to orange. David et al. (2001) have identified lepidocrocite as a component of yellow ochres q.v.) used at Tell el Amarna. Wainwright et al. (2002) and Watchman et al. (1993) have detected it from rock paintings in Argentina and North Queensland, Australia, respectively. 

According to Carlyle s survey of nineteenth century British documentary sources, Spanish ochre was a synonym for Mars orange q.v.), a synthetic iron oxide pigment (Carlyle, 2001). Salter (1869) however explicitly links it to a burnt yellow or Roman ochre (. v.). It should also be noted that there were commercially important deposits of a red ochre (. v.) known as Spanish red. 

The most important synthetic routes to iron oxide pigments involve either thermal decomposition or aqueous precipitation processes. A method of major importance for the manufacture of a-Fe203, for example, involves the thermal decomposition in air of FeS04-7H20 (copperas) at temperatures between 500 °C and 750 °C. The principal method of manufacture of the yellow a-FeO(OH) involves the oxidative hydrolysis of Fe(n) solutions, for example in the process represented by reaction (1). 

Iron Oxide Red, pigment for plastics, 7 370t Iron oxide reds, synthetic, 19 398-399 Iron Oxide Yellow, pigment for plastics, 7 370t... 

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