Iron pigments

Metallic iron pigments are commercially produced by the reduction of acicular (needle-shaped) iron compounds [5.21]. As in the production of magnetic iron oxide pigments, the starting materials are iron oxide hydroxides (see Section 3.1.1) or iron oxalates, which are reduced to iron in a stream of hydrogen either directly or via oxidic intermediates. 

Due to their high specific surface area, metallic pigments are pyrophoric, so that passivation is necessary. This can be achieved by slow, controlled oxidation of the particle surface [5.22]. 

Metallic pigments have a higher specific surface area (up to 60 m2/g) and a higher saturation magnetization than oxidic magnetic pigments. Their capacity for particle alignment corresponds to that of the oxides (see Section 5.1.1, Table 36). 

Economic Aspects. The largest producers of metallic iron pigments are Dowa Mining, Kanto Denka K., and Mitsui Toatsu. 

World consumption in 1995 was ca. 1800t, of which ca. 75% was used in the manufacture of video tapes ca. 14% for audio and 11 % for data storage applications. Consumption is expected to increase. 

---

In general, all iron pigments are characteri2ed by low chroma and excellent Hghtfastness. They are nontoxic, nonbleeding, and inexpensive. They do not react with weak acids and alkaHes, and if they are not contaminated with manganese, do not react with organic solvents. However, properties vary from one oxide to another. 

See Iron Pigments, inorganic Sulfur Sulfuric acid and sulfur trioxide. 

Reh, n, roe (deer), doe, buck, -braun, n. velvet brown (an iron pigment) fawn color, reh-braun, -farben, -farbig, a. fawn-colored. Reh-ledcr, n. doeskin buckskin chamois. 

Hevesy first used a radioisotope as a tracer. Warburg. Importance of iron pigments in oxidation. Keilin rediscovered cytochromes. Sumner crystallized urease. The Eggletons and Fiske and SubbaRow isolated phospho-creatine. 

A number of electrochemical processes involving solid materials can be described in terms of the reductive or oxidative dissolution of such materials. Within this type of processes, one can include the stripping of metal deposits previously mentioned. In the context of archaeometry, conservation, and restoration sciences, the reductive dissolution of iron oxide-type materials is of particular interest. Thus, application of the voltammetry of the microparticles approach for identifying iron pigments has been described [108, 137-139]. 

Grygar T, Bezdicka P, Hradil D, Domenech A, Marken F, Pikna L, Cepiia G (2002) Voltam-metric analysis of iron pigments. Analyst 127 1100-1107. 

Pliny uses the word minium to denote our cinnabar. In describing rubrica, a red iron pigment, he says,... 

Scrap iron - [PIGMENTS - INORGANIC] (Vol 19) -for copper cementation [COPPER] (Vol 7)... 

Iron Oxide Pigments. In general, all iron pigments are characterized by... 

With this, the complex iron pigment does indeed deserve to be called insoluble, as only one part of dissolved Iron Blue can statistically be found in 100,000,000,000,000,000,000,000,000,000 parts of water (1029). The actual solubility would therefore be less by a factor of 102° as determined by Tananaev el al., which would come pretty close to values calculated for other so-called insoluble compounds, like mercury sulfide (HgS). However, one must consider that the chemistry of Fe3+ in aqueous solutions doesn t justify the terms dissolved or precipitated , since a multitude of complexes do exist in the... 

This process would have been replaced much earlier by more economical reduction methods if it had not been possible to obtain valuable iron oxide pigments from the iron oxide sludge. However the increasing demand for aniline has far surpassed the market for iron pigments, so this process is no longer preferred46. 

Neilands, J. B. A crystalline organo-iron pigment from a fungus, Ustilago sphaerogena. J. Am. Chem. Soc. 74, 4846 (1952). 

The largest producers of metallic iron pigments are Dowa Mining and Toda Kogyo (Japan). World consumption in 2002 was ca. 1800 t, of which ca. 65% were used in the manufacture of broadcasting media, 2% for audiotapes, and 33% for data storage applications this last being expected to increase later. 

Fig. 5.2 TEM-photographs showing typical morphology of metallic iron pigments (Table 5.1). A) Iron pigment for lEC IV compact cassettes (metal operating point). B) Iron pigment, for digital audio (R-DAT) 8 mm video tape, data storage.

---