Iron colours

Iron-coloured Bavarian clay, with which those furnaces are coloured wherein iron is treated. An iron-grey sand. 

Native In mountains and rivers. Described by Galenus. Said to be the German Iris. Fossile, from mines. Otherwise, Cobalt. If this there are three kinds I. Black, 2. Grey-ashen, 3. Iron colour. 

Pure Iron of an iron colour, found in seams in a white flint. 

Dense, iron-coloured, masculine, Misnensian Magnet, mined at Swartzburg. 

An iron-colour Schist or Bloodstone, easily divided into long sections. 

Wedge-shaped, iron-coloured Bohemian Bloodstone. 

A hard greyish Stone with an outer surface of iron-colour. 

Emery, iron-coloured, and harder than iron. 

Onolsbach, crustaceous, iron-coloured, of which leaves of tables are made. 

Bohemian, iron-coloured, mixed with brass, which appears like minute scales. 

Various kinds of Pyrites are found in our mines-Silver Colour, almost Gold Colour, True Gold Colour like Galena, Ashen Colour, and Iron Colour. 

Iron-coloured Pyrites is mentioned by Avicenna. It is found in certain iron mines. The miners call it Iron Stone, not that it is actually such, but is like it. From most of these six species fire can be struck. Some of them are very heavy, and are more adapted for striking fire, as Pliny observes. Some distinguish a special genus of Pyrites, which abounds in fire, and is called Live Pyrites. We may, indeed, deny that there is any other genus. Those species which are dense and compact, as the first two, abound in fire. The looser the texture, the more subtle and the more broken up, the less fire can be elicited. Albertus, though a man wise in his time, makes extraordinary mistakes about... 

Vogel s Red. A pure ferric oxide produced by precipitating ferrous oxalate which is then calcined. It has been used as a basis for some iron colours on porcelain. 

Group III with electronic configuration 5s 4d . The principal ore is gadolinite (a silicate also containing lanthanides). Y2O3 containing Eu is used as a red phosphor in colour television. Yttrium iron garnets are used as microwave filters. 

Among the metals, for example, sodium and potassium are similar to each other and form similar compounds. Copper and iron are also metals having similar chemical properties but these metals are clearly different from sodium and potassium—the latter being soft metals forming mainly colourless compounds, whilst copper and iron are hard metals and form mainly coloured compounds. 

When M is a voltmeter an indication of the energy difference between the reactants and products is obtained (see below). A current passes when M is an ammeter, and if a little potassium thiocyanate is added to the Fe (aq) a red colour is produced around the electrode, indicating the formation of iron(III) ions in solution the typical bromine colour is slowly discharged as it is converted to colourless bromide Br . 

Evidence for the solvated electron e (aq) can be obtained reaction of sodium vapour with ice in the complete absence of air at 273 K gives a blue colour (cf. the reaction of sodium with liquid ammonia, p. 126). Magnesium, zinc and iron react with steam at elevated temperatures to yield hydrogen, and a few metals, in the presence of air, form a surface layer of oxide or hydroxide, for example iron, lead and aluminium. These reactions are more fully considered under the respective metals. Water is not easily oxidised but fluorine and chlorine are both capable of liberating oxygen ... 

The thiocyanate ion SCN forms an intensely red-coloured complex (most simply represented as [Fe(SCN)(H20)5] ) which is a test for iron(III). However, unlike cobalt(III), iron(lll) does not form stable hexammines in aqueous solution, although salts containing the ion [FefNHj) ] can be obtained by dissolving anhydrous iron(III) salts in liquid ammonia. 

Add a little of the sodium derivative to about 5 ml. of water in a test-tube, followed by a drop of ferric chloride solution. A deep red colouration is produced but rapidly disappears as the iron is precipitated as ferric hj droxide. 

Place 84 g. of iron filings and 340 ml. of water in a 1 - 5 or 2-litre bolt-head flask equipped with a mechanical stirrer. Heat the mixture to boiling, stir mechanically, and add the sodium m-nitrobenzenesulphonate in small portions during 1 hour. After each addition the mixture foams extensively a wet cloth should be applied to the neck of the flask if the mixture tends to froth over the sides. Replace from time to time the water which has evaporated so that the volume is approximately constant. When all the sodium salt has been introduced, boU the mixture for 20 minutes. Place a small drop of the suspension upon filter paper and observe the colour of the spot it should be a pale brown but not deep brown or deep yellow. If it is not appreciably coloured, add anhydrous sodium carbonate cautiously, stirring the mixture, until red litmus paper is turned blue and a test drop upon filter paper is not blackened by sodium sulphide solution. Filter at the pump and wash well with hot water. Concentrate the filtrate to about 200 ml., acidify with concentrated hydrochloric acid to Congo red, and allow to cool. Filter off the metanilic acid and dry upon filter paper. A further small quantity may be obtained by concentrating the mother liquid. The yield is 55 g. 

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