Chromium oxides, names

Metal oxides usually consist of bulk oxides. As semiconductors, metal oxides catalyze the same kind of reactions as metals but in processes requiring higher temperatures. Often a mixture of various oxides is applied to increase the catalytic activity. For example, transition metals, such as M0O3 and Cr203, are good catalysts for polymerization of olefins a mixture of copper and chromium oxides, named copper chromite, is used for hydrogenation and a mixture ofiron and molybdenum oxide (ie, iron molybdate), is used for formaldehyde formation from methanol. 

Aluminum oxide, which has the mineral name corundum, is a solid that has several important uses. Because it will withstand very high temperatures, it is a refractory material, and because of its hardness it is commonly used in abrasives. Corundum often contains traces of other metals that impart a color to the crystals, making them valuable as gemstones. For example, ruby contains a small amount of chromium oxide, which causes the crystal to have a red color. By adding a small amount of a suitable metal oxide, it is possible to produce gemstones having a range of colors. 

Four years later, in 1805, the Collet-Descotils examined what was supposed to be the metal, stating it was just an impure chromium oxide. Del Rio apparently accepted this conclusion. In 1830 the Swedish chemist N.G. Seftroem discovers a new metal which he named VANADIUM. This metal was described by Berzelius in 1831, as follows ... 

Emerald Green em-r9ld gren n (1646) Name applied to two distinctly different green pigments complex copper acetoarsenite (also known as Paris Green and Schweinfurt Green) and chromium hydroxide. See Hydrated Chromium Oxide. 

Synonym, variant or common name See chromium oxide. 

Guignet s green is a synonym for viridian (chromium oxide hydrate), the term deriving from the name of the French chemist who in 1859 patented the method still generally used for its manufacture (Newman, 1997). Riffault et al. (1874) give two recipes attributed to Guignet. The term was stiU apparently current at the time Heaton was writing (1928). 

Pannetier s green is a synonym for a chromium oxide hydrate pigment, viridian (. v.), described as a sesquioxide of chromium prepared in a particular manner by Riffault et al. (1874). The name derives from a Parisian colour maker who, along with his assistant Binet, first prepared it about 1838 (Church, 1901). 

Potter s pink was manufactured from tin oxide roasted with chalk and small amounts of chromium oxide qq.v.) to produce a range of pink shaded pigments. It is also known as mineral lake and tin pink (Mayer, 1991). Burton (1907) states that this is the name given by the Society of Painters in Tempera to a potter s colour first prepared in the early nineteenth century. 

Vernalis was the name given by the Society of Tempera Painters to a pigment made by heating chalk and viridian (chromium oxide hydrate) with a trade name of Victoria green (a mixed green of viridian and zinc yellow however, probably of variahle composition). This was a potter s pigment recommended for use by the Society for Painters in Tempera for use with tempera and fresco (Burton, 1907). 

However, compounds known to be double oxides in the solid state are named as such for example, Cr2Cu04 (actually Cr203 CuO) is chromium(III) copper(II) oxide (and not copper chromite). 

Finally, in 1797, the Frenchman L. N. Vauquelin discovered the oxide of a new element in a Siberian mineral, now known as crocoite (PbCr04), and in the following year isolated the metal itself by charcoal reduction. This was subsequently named chromium (Greek xpco ia, chroma, colour) because of the variety of colours found in its compounds. Since their discoveries the metals and their compounds have become vitally important in many industries and, as one of the biologically active transition elements, molybdenum has been the subject of a great deal of attention in recent years, especially in the field of nitrogen fixation (p. 1035). 

In compounds, the important oxidation numbers of Cr are +2, +3, and +6. In all of these states the chromium ions are colored and, in fact, the element got its name from this property (ichroma is the Greek word for color). The +2 state is not frequently encountered but it can be made quite easily as the beautiful blue chromous ion in solution by dripping a solution containing CrM over metallic zinc. Air has to be excluded since O rapidly converts Cr1-5 back into Cr. ... 

Cr03 As a transition metal, chromium forms more than one stable cation. Name the metal first, using a Roman numeral to designate chromium s charge. Each of the three oxide anions has a -2 charge. To maintain net charge neutrality, Cr must be +6, so the name of the compound is chromium(VI) oxide. 

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