Blue iron pigments

Iron Blue, Cl Pigment Blue 27, which has been known by various names over the years, perhaps the best known being Prassian Blue, is ferric ammonium ferricyanide, FeNH Fe(CN)g(xH20. The hrst step in its preparation involves the precipitation of complex iron(ii) cyanides, e.g. potassium hexacyanoferrates(ii) with iron(i) salts, e.g. the sulfate or chloride, in an aqueous solution in the presence of ammonium 

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Chrome green is produced by mechanically mixing chrome yellow and iron blue pigments in water. An iron blue, [Fe(NH4) (FeCN6)], is an oxidized precipitate product of the reaction between an aqueous solution of iron sulfate and ammonium sulfate with sodium hexacyanoferrate. 

Iron blacks, 79 401-402 Iron blast furnace, 76 141-143 Iron Blue, pigment for plastics, 7 370t Iron blue pigments, 79 407 Iron(II) bromide, 74 539 Iron(III) bromide, 74 539-540 Iron brown hematite, formula and DCMA number, 7 347t Iron browns, 79 402 Iron carbide, 4 649t, 690—692 lattice, 4 652... 

Molybdates/lead chromates Luster pigments Mixed metal oxide pigments Iron blue pigments Ultramarine... 

The term iron blue pigments as defined in ISO 2495 has largely replaced a great number of older names (e.g., Paris blue, Prussian blue, Berlin blue, Milori blue, Turnbull s blue, toning blue, and nonbronze blue). These names usually stood for insoluble pigments based on microcrystalline Fe(II)Fe(III) cyano complexes many were associated with specific hues. A standardized naming system has been demanded by users and welcomed by manufacturers, and has led to a reduction in the number of varieties [3.177],... 

X-ray and infrared spectroscopy show that iron blue pigments have the formula MIFe11Fem(CN)6 H20 [3.179]. M1 represents potassium, ammonium, or sodium, of which the potassium ion is preferred because it produces excellent hues in industrial manufacture. 

Iron blue pigments are produced by the precipitation of complex iron(II) cyanides by iron(II) salts in aqueous solution. The product is a whitish precipitate of iron(II) hexacyanoferrate(II) M 2Fe1I[Fe1I(CN)6] or M11Fe11[Fe11(CN)6], (Berlin white), which is aged and then oxidized to the blue pigment [3.180]. 

For quality standards, see Table 1 ( Iron blue pigments Methods of analysis and Specification ). 

Due to their small particle size (see Table 26 and Figs. 38 and 39), iron blue pigments are very difficult to disperse. A graph of cumulative particle size distribu-... 

Table 26. Physical and chemical properties of iron blue pigments (VOSSEN BLAU and MANOX Blue grades)... 

Figure 38. Electron micrograph of an iron blue pigment of small particle size (Manox Blue 460 D)...

Figure 40. Cumulative particle size distribution curve of a normal (705) and a mi-cronized (705 LS) iron blue pigment of equal primary particle size LS = Luftstrahlmiihle (air jet mill)...

Figure 41. Residual gloss and AE%b values for isocyanate-cross-linked polyacrylate resins that contain 15wt% Vossen Blau 2000 (older pigment type which has been replaced by Manox Blue 460 D) relative to the binder and 15 wt% Ti02 (rutile) relative to the iron blue pigment after 1000 h fast exposure to UV [3.193] a) Without clearcoat b) With clearcoat but without UV protection c) With clearcoat and UV protection...

Iron blue pigments are thermally stable for short periods at temperatures up to 180 °C, and therefore can be used in stoving finishes. The powdered material presents an explosion hazard, the ignition point is 600-625 °C (ASTM D 93-52). The pigments are combustible in powder form, ignition in air being possible above 140 °C [3.180],... 

Total production of iron blue in 1975 was ca. 25000 t/a, but in 1995 it was only ca. 13000-15000 t/a. The main consumer in Europe and USA is the printing ink industry. The second largest use in Europe, especially of micronized iron blue pigments, is for coloring fungicides, but use in the paint industry is decreasing. 

Iron blue pigments are used in the manufacture of single- and multiple-use carbon papers and blue copying papers, both for toning the carbon black and as blue pigments in their own right [3.180]. 

In the following section, the coloristic effects of those iron blue pigments are described, as obtained in toning experiments involving a LCF-type carbon black, in comparison with Pigment Blue 15 3 and Pigment Blue 61. 

Paints and Coatings. Iron blue pigments are used in the paint industry, especially for full, dark blue colors for automotive finishes. A full shade with good hiding power is produced by 4-8% iron blue pigments. 

Paper. Blue paper can be produced by adding water-soluble iron blue pigment directly to the aqueous phase. Alternatively, a suitable iron blue pigment can be ground together with a water-soluble binder, applied to the paper, dried, and glazed (quantity applied ca. 8% in the dispersion). 

Toxikokinetic studies showed, that the adsorption of iron blue pigments is very low. Following intravenous injection of a 59Fe-radio labelled iron blue pigment, the [59Fe(CN)6]4 ion was rapidly and virtually completely excreted with the urine. After oral administration of ferric cyanoferrate (59Fe) approx. 2% of the labelled... 

Fe4[Fe(CN)6] can bind caesium therefore iron blue pigments are used in clinical practice as an antidote for the treatment of humans contaminated with radioactive caesium (see also Section 3.6.4). Clinical use of iron(III) ferrocyanide in doses up to 20 g/d for decontaminations of persons exposed to radio caesium has not been associated with any reported toxicity [3.209]. 

There are no harmful effects on fish, but the toxic effects on bacteria constitute a slight hazard when iron blue pigments are present in water. 

Trade names include Manox Iron Blue (Manox, UK), and Vossen-Blue 2000 (De-gussa, Germany). Transparent iron blue pigments are also produced by Dainichi-seika (Japan). 

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