Cobalt oxides blue pigments

Regulated Colorants That Are FDA Approved. It often seems a contradiction that many of the colorants that are suitable for use in food contact applications must also appear on an MSDS as a reportable or hazardous material. Examples include zinc oxide and zinc sulfide, both zinc compounds chromium oxide green (pigment green 17), a chromium compound carbon black and cobalt aluminate blue (pigment blue 28), which is not only reportable because of its cobalt content but is also a suspected carcinogen. 

Cobalt ores are often found in association with copper(II) sulfide. Cobalt is a silver-gray metal and is used mainly for alloying with iron. Alnico steel, an alloy of iron, nickel, cobalt, and aluminum, is used to make permanent magnets such as those in loudspeakers. Cobalt steels are hard enough to be used as surgical steels, drill bits, and lathe tools. The color of cobalt glass is due to a blue pigment that forms when cobalt(II) oxide is heated with silica and alumina. 

Cobalt blue [ColAlO lj], also known as cobalt ultramarine or azure blue, is a compound of aluminum oxide and cobalt. It is used as a pigment that mixes well with both oil and water. It also has cosmetic uses for eye shadow and in grease paint. Cobalt blue is one of the most durable blue pigments in that it resists weathering in paints and holds up to other wear and tear. 

Inorganic pigments are found in the earth. Iron and lead oxides provide earth colors. Copper calcium silicate and cobalt stannate provide blues. The colors burnt sienna and burnt umber come from iron oxides. Green pigments come from chromic oxide, calcinated cobalt, and zinc and aluminum oxides. Red pigments come from cadmium sulfide, cadmium selenide, and barium sulfate. All these chemical compounds come from the earth. 

Paints are a mixture of particles of pigment in a liquid base. Once the liquid evaporates, the pigment particles coat a painted surface. Transition elements and their compounds are often used as paint pigments. Iron oxides are used as red, yellow, and brown pigments. Chromium, copper, and cobalt compounds produce green and blue pigments. Titanium dioxide is often used for white paint. 

Pigments for use with concrete in the UK should comply with BS 1014. Carbon black, red, yellow, brown and black iron oxides, black manganese oxide, blue cobalt oxide and green chromium oxide are used. 

Fe, Co, Ni. This provides a range of colours in which the excellent durability characteristics of the host crystal structures are retained. An important commercial example of a mixed oxide pigment based on the spinel lattice is cobalt aluminate blue (Cl Pigment Blue 28), which is usually represented as C0AI2O4,... 

This body has devised a scheme for the classification of pigments, based on the chemical and structural identity of the colouring substance. It excludes single metal oxides and non-oxide pigments (q.v.) but includes all mixed metal oxides in one of 14 crystal classes and over 50 pigment categories, each having a specific DCMA Number (E.g. Crystal class XIII is spinel and DCMA No 13-26-2 refers to cobalt aluminate blue spinel. 

King s Blue. A blue pigment, being mixed cobalt oxide and alumina. 

Smalt or Powder Blue. A fused mixture of cobalt oxide, sand and a flux, e.g. potash. It is sometimes used as a blue pigment for the decoration of pottery or for the colouring of glass or vitreous enamel (cf. zaffre). 

The arsenic traces derive from ores used during the preparation of cobalt oxide. The silicon and potassium signals are typical of potassium glass. All of these elements are, thus, an important factor in the discrimination of this pigment from other blue pigments. 

Combinations of cobalt(II) oxide and aluminum oxide in the spinel stoichiometry give cobalt aluminate blue spinels, C0AI2O4, C.I. Pigment Blue 28. Variations of this pigment include modification by zinc (C.I. Pigment Blue 72), magnesium, titanium, and lithium oxides. If lithium and titanium modifiers are added, a turquoise blue pigment is obtained. 

Cobalt Blue n (1835) Co0-Al203. Pigment Blue 28 (77346). Bright blue pigment, which is a complex product derived from oxides of cobalt and aluminum. It has excellent lightfastness and good chemical and heat resistance and with low opacity. Density, 4.2-4.3 g/cm (35.0-35.8 Ib/gal) O.A., 27-36 particle size, 0.5-1.0 pm. Syn Azure Blue, Cobalt Aluminate, Cobalt Ultramarine, Dumont s Blue, Enamel Blue,... 

Also included here are the secondary oxides (aluminates) calcium aluminate (CaAl204), cobalt aluminate (C0AI2O4), lead aluminate (PbAl204) and hercynite (iron aluminate, Fe Al204). Calcium aluminate (calciiun aluminium oxide) may be a component of the pigment known as Satin white. Cobalt aluminate (cobalt aluminium oxide) is the pigment Cobalt blue. Lead alu-minate is listed by the Colour Index (1971) under Cl 77585. Hercynite has been identified on Minoan painted pottery by Stos-Fertner et al. (1979). Chromium aluminium cobalt oxide is Turkish Green. 

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