Iron chromates

Iron-carbon phase diagram, 76 196-197 Iron castings, tellurium in, 24 424 Iron(II) chloride, 74 538 Iron(III) chloride, 74 539 Iron(III) chloride hexahydrate, 74 539 Iron(II) chloride tetrahydrate, 74 538 Iron Chromate Black, pigment for plastics, 7 369t... 

Catalysts, desiccants, and catalyst inerts. In 1988, the refinery began to recycle nonhazardous catalysts, desiccants, and catalyst fines. It recycles electrostatic precipitator fines, Claus catalyst, and catalyst support inerts for use in cement manufacture. Two other catalysts, zinc oxide and iron chromate from the hydrogen plant, are reprocessed at smelters to recover the metals. 

In the same year Mining Superintendent von Soymonof had found some of this mineral in the northern part of the Ural Mountains. When Lowitz analyzed it, he concluded that it must be iron chromate... 

Amongst the oxides mixed with earthy matter, may be classed chromate of iron, chromate of baryta, chromate of lead, chloride of silver, purple of caBsins, umber, sienna, and red and yellow ochres. The mode of preparation of these various materials causes the greatest difference in the quality of the colors into which they severally enter. 

Iron Chromates.—Ferrous chromate does not appear to be capable of existence. When solutions of ferrous sulphate and chromic acid, or its alkali salts, are mixed at low temperatures, the iron is oxidised, basic ferric sulphates resulting, the chromium being correspondingly reduced. If the ferrous sulphate is in excess, ferroso-ferric sulphate results. 

Passivation Inhibitors. Examples of passivators (anodic inhibitors) include chromate, nitrite, molybdate, and orthophosphate. AH are oxidizers and promote passivation by increasing the electrical potential of the iron. Chromate and nitrite do not require oxygen, and thus, can he the most effective. Chromate is an excellent aqueous corrosion inhibitor, particularly from a cost perspective. However, owing to health and environmental concerns, use of chromate has decreased significandy and will probably he outlawed soon. Nitrite is also an effective inhibitor, but in open systems it tends to be oxidized to nitrate. 

Iron chromate (as the mineral chromite) has to be powdered extremely finely and then fused in a nickel crucible with sodium peroxide. First melt about 1 g of solid Na202 in a nickel crucible by very gentle heating, allow to cool and add 10-50 mg of the mineral. Heat the mixture gently until the fusion is complete. Leach the cooled metal with hot water until the mixture dissolves. Remove the crucible and carefully acidify the solution with 6m hydrochloric acid. The metal hydroxides should dissolve completely the solution is green because of the presence of nickel ions, originating from the walls of the crucible. Iron(III) and chromium can be tested in the solution (cf. Sections 3.22 and 3.24). Examine the crucible and discard it if the walls are worn thin. 

Bismuth chromates group Calcium chromates group Copper chromates group Iron chromates group Lead chromates group Zinc chromates group Barium chromate(VI) Barium potassium chromate Cadmium chromate Crocoite Manganese chromate Mercury chromate Silver chromate Strontium chromate Thallium chromate Tin chromate... 

Iron chromates group Iron dichromate Colour Index (1971) 77505 Kuhn Curran (1986)... 

According to the chemical literature, iron(III) dichromate(VI), Fe2(Cr207)3, is used as a water-soluble pigment and is obtained by heating aqueous chromic acid with hydrous iron(III) oxide Colour Index, 1971 MacIntyre, 1992). Related compoimds also used as pigments are iron chromate, Fe2(Cr04)3, and iron chromate hydroxide, Fe(OH)Cr04 (qq.v.). 

It was termed Sideringelb by Kletzinsky (1872), who is associated with early manufacturing of iron chromate. 

Copper chromate oxide hydrate Cobalt chromate Iron dichromate Iron chromate hydroxide Manganese chromate hydrate Silver chromate Thallium chromate Titanium chromate Cadmium chromate Cadmium chromate hydroxide Mercury chromate Zinc dichromate hydrate Zinc chromate(VI) hydroxide Zinc sodium chromate Zinc potassium chromate... 

In numerous cases, known as reciprocal solutions, the solid solution can be considered to be the product of two pairs of pure compounds, which are called the poles. Thus, the solution between iron sesquioxide (Fc304) and nickel chromate (NiCr204) 5delds spinel (Fe, Ni )i (Cr, Fe )i. However, this solution could also give rise to the following pure compounds iron chromate (FeCr204) and nickel ferrite (NiFe04). We say that the possible poles of spinel are either the iron sesquioxide-nickel chromate pair or the iron chromate-nickel ferrite pair. 

---