Iron volatilisation

Arsenic(III) sulphide, As2S3 Discussion. The arsenic must be present as arsenic(III), In this condition [ensured by the addition of, for example, iron(II) sulphate, copper(I) chloride, pyrogallol, or phosphorous(III) acid] arsenic may be separated from other elements by distillation from a hydrochloric acid solution, the temperature of the vapour being held below 108 °C arsenic trichloride (also germanium chloride, if present) volatilises and is collected in water or in hydrochloric acid. 

Estimation of Selenium in Sulphide Minerals.s—In various sulphite-cellulose manufactories difficulties have occurred which have been traced to the presence of selenium in the pyrites used for burning. Part of the selenium remains in the burnt pyrites and part volatilises with the sulphur dioxide. 20 to 30 grams of pyrites are dissolved in hydrochloric acid (dens.=1-19) and potassium chlorate. Zinc is added to reduce the iron to the ferrous condition more hydrochloric acid is then added, the solution boiled and stannous chloride added to precipitate selenium. Since the selenium may contain arsenic, it is collected on an asbestos filter, dissolved in potassium cyanide and reprecipitated using hydrogen chloride and sulphur dioxide. The element may then be estimated by the iodometric method described below. In order to determine the relative proportion of volatile to non-volatile selenium, the pyrites may be roasted in a current of oxygen. After this treatment the contents of the tube are dissolved in warm potassium cyanide and the selenium reprecipitated and estimated in the ordinary way. 

Method I.—The apparatus described in Preparation 1 is fitted up, a 500-c.c. flask being used, and 30 gms. (1 mol.) of finely powdered tartaric acid, 150 gms. (excess) of absolute alcohol, and 50 gms. of crystallised benzene placed in the flask. The object of the benzene is to help to volatilise the water produced by forming with it and the alcohol the low boiling ternary system—alcohol-benzene-water. The iron tube is packed with small lumps of good quicklime, and is heated to a temperature of 90°. The mixture in the flask is boiled, a few pieces of porous porcelain being added to promote steady ebullition. Esterification proceeds almost to completion, owing to the removal by the quicklime of the water formed. After 6 hours, the liquid in the flask, which will have become quite viscid owing to the formation of the ester, is distilled on a water bath until all the benzene and excess of alcohol have been removed the residue is fractionated from a metal bath under reduced pressure. 

Rhodium readily alloys with platinum, stiffening it and yielding mixtures that are useful for a variety of laboratory purposes. Rhodium reduces the loss in weight of platinum by volatilisation at all temperatures above 900° C., and it has therefore been suggested that a useful alloy for best quality crucibles would be platinum containing 3 to 5 per cent, of rhodium, practically free from iron and iridium, and containing no other detectable impurities. 2... 

Another chemical interference encountered in AAS is that with chromium determinations where the chromium absorption in an air—acetylene flame is suppressed by iron, cobalt and nickel. In this instance, the iron interference can be minimised by the addition of 2% (m/v) ammonium chloride solution to the sample and standard solutions. This compound helps volatilise the chromium as chromyl chloride (Cr02Cl). 

Moissan succeeded in volatilising iron in his electric furnace with a current of 350 amperes at 70 volts. In a few minutes a sublimate or distillate of iron was obtained on a water-cooled tube 4 as a grey powder mixed with some brilliant and malleable scales, and possessed of the same chemical properties as the finely divided metal. The distillation of iron in this manner is difficult on account of the violent frothing caused by the boiling metal evolving occluded gases.5... 

Iron is readily corroded by moist chlorine at atmospheric temperatures, and when strongly heated in a current of the dry gas yields ferric chloride, which volatilises and condenses on a cooler part of the apparatus in a beautifully crystalline form. 

It volatilises at 1100° C., and is reduced by hydrogen at high temperatures to metallic iron. It dissolves slowly in water, and the solution gradually deposits hydrated ferric oxide. 

Ferric chloride, FeCl3, occurs in nature in the lava of Vesuvius, as the mineral molysite. In the laboratory it is prepared in the anhydrous condition by passing a rapid current of dry chlorine through a retort over heated iron wire, advantageously cut into pieces some 6 mm. in length. The ferric chloride volatilises and condenses as beautiful crystals on the upper, cooler portions of the retort. 

Ferrous selenide was first obtained by Divers and Shimidzu 9 by heating a mixture of wrought-iron filings and selenium in a graphite pot. When the mixture had grown hot, a considerable portion of the selenium had volatilised and a further portion was added which combined with the iron with very little loss, causing vivid ignition and complete liquefaction. The product thus obtained closely resembles iron sulphide. It is not very sensitive to acids, but when warmed with... 

Several compounds of iron and carbon monoxide are known. Mond and Quincke6 were the first to obtain experimental evidence of the existence of volatile iron carbonyls they succeeded in volatilising reduced iron in a current of carbon monoxide to a very slight extent, and concluded that a tetracarbonyl, Fe(CO)4, had been produced corresponding to the nickel analogue, Ni(CO)4, which had been prepared the previous year.7 A few months later Mond and Danger 8 succeeded m isolating the iron carbonyl, and found it to be not the tetra but the penta derivative. 

A method, suitable for the analysis of molybdates and molybdenum ores, consists in heating the substance at 400° to 560° C. in a stream of carbon tetrachloride vapour, when molybdic acid volatilises and may be collected in a receiver, evaporated with nitric acid, ignited, and weighed. If iron is present it also volatilises, and must be separated from the condensed product. 

High levels of sodium and potassium can volatilise and contribute to the formation of rings in rotary kilns (see section 16.4.9). High levels of silica, alumina and iron oxide (e.g., 5 to 10 %) can cause fusion leading to crotches (also known as scaffolds and bears ) in shaft kilns [14.5], They can also contribute to rings and clinkering in rotary kilns. Where the lime is to be supplied to the steel industry, sulfur levels above 0.01 % S in the stone may either restrict the fuel/kiln options, or render the lime unsuitable (see section 27.4.3). 

On the action of fire animated by vital air on the most refractory minerals in which it is shown that all metals except platinum volatilise, gold and silver much more slowly than others, that some metals are incombustible, whilst others burn with a very marked flame, and that iron burns rapidly, throwing out a shower of sparks the use of oxygen in cupellation is advised. 

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