Inorganic pigments iron oxides

Pigments are classified as organic or inorganic. Organic pigments are brighter, less dense, and smaller in particle size than the more widely used, more opaque, inorganic colorants. Iron oxides or ochers are available as yellow, red, black, brown, and tan. 

Chemical Composition. With few exceptions, inorganic pigments are oxides, sulfides, oxide hydroxides, silicates, sulfates, or carbonates (see Tables 3 and 4), and normally consist of single-component particles (e.g., red iron oxide, a-Fe203) with well defined crystal structures. However, mixed and substrate pigments consist of nonuniform or multicomponent particles. 

Consumer articles often use colorants (qv), reodorants, or finishing agents. Carbon black (qv) provides the best technological properties for industrial appHcations, so most mbber articles are black. Red iron oxide or other inorganic pigments are used to color mineral-filled articles. Organic... 

Because of the high processing temperatures there are few pigments suitable for use with PTFE. A number of inorganic pigments, particularly the cadmium compounds, iron oxides and ultramarines, may, however, be used. 

Inorganics are denser and usually of a larger particle size. Common inorganic pigments include iron oxides in buff colors, titanium dioxide in white, lead and zinc... 

Some inorganic compounds are used as food additives and food colorants. They include titanium dioxide, carbon black, iron oxides, ultramarin, and calcium carbonate. Some of them are important for properties other than the ability to impart color. Titanium is the most commonly used inorganic pigment in food and will be briefly discussed below. ° "°... 

The presence of mica in pearlescent pigments only partly accounts for the appearance of the pigment. A very thin layer of the inorganic oxide titanium dioxide (TiC>2) or iron oxide (Fe2C>3) or both is coated on the mica platelets. The various colors and pearlescent effects are created as light is both refracted and reflected from the titanium dioxide layers. The very thin platelets are highly reflective and transparent. With their plate-like shape, the platelets are easily oriented into parallel layers as the paint medium is applied. Some of the incident light is reflected... 

Commonly, blends of organic pigments with suitable inorganic pigments are used, such as nickel titanium yellow, chrome titanium yellow, bismuth-molybdenum-vanadium-oxide, or iron oxide. 

Buxbaum, G. Printzen, H. (1992) Iron oxide pigments. In Ullmanris encyclopedia of industrial chemistry. Pigments, inorganic. Vol. A20,VCH Weinheim, 297-304... 

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