Other Iron Removal Media

I.G. Farbeninduslrie, Rheinpreussen, and others—modification of medium-pressure synthesis with iron catalysts (hot-gas recycle, oil slurry, oil recycle). Hot gas recycle. As already discussed, recycle operations (with removal of liquid reaction products after each step) with a ratio of recycle gas to fresh feed of 1 1 tconsumption ratio of hydrogen to carbon monoxide, increase in some cases the olefin content of the products and the total yields, and result in a smoother operation which can be important for the lifetime of the catalysts. 

Discussion. Minute amounts of beryllium may be readily determined spectrophotometrically by reaction under alkaline conditions with 4-nitrobenzeneazo-orcinol. The reagent is yellow in a basic medium in the presence of beryllium the colour changes to reddish-brown. The zone of optimum alkalinity is rather critical and narrow buffering with boric acid increases the reproducibility. Aluminium, up to about 240 mg per 25 mL, has little influence provided an excess of 1 mole of sodium hydroxide is added for each mole of aluminium present. Other elements which might interfere are removed by preliminary treatment with sodium hydroxide solution, but the possible co-precipitation of beryllium must be considered. Zinc interferes very slightly but can be removed by precipitation as sulphide. Copper interferes seriously, even in such small amounts as are soluble in sodium hydroxide solution. The interference of small amounts of copper, nickel, iron and calcium can be prevented by complexing with EDTA and triethanolamine. 

The cobalt complex is usually formed in a hot acetate-acetic acid medium. After the formation of the cobalt colour, hydrochloric acid or nitric acid is added to decompose the complexes of most of the other heavy metals present. Iron, copper, cerium(IV), chromium(III and VI), nickel, vanadyl vanadium, and copper interfere when present in appreciable quantities. Excess of the reagent minimises the interference of iron(II) iron(III) can be removed by diethyl ether extraction from a hydrochloric acid solution. Most of the interferences can be eliminated by treatment with potassium bromate, followed by the addition of an alkali fluoride. Cobalt may also be isolated by dithizone extraction from a basic medium after copper has been removed (if necessary) from acidic solution. An alumina column may also be used to adsorb the cobalt nitroso-R-chelate anion in the presence of perchloric acid, the other elements are eluted with warm 1M nitric acid, and finally the cobalt complex with 1M sulphuric acid, and the absorbance measured at 500 nm. 

It is usually sufficient to differentiate only between small or medium salt contents—up to about 300 mg/L, as in drinking water and waters of higher salt contents. [Note that 1 mg/L = 1 part per million (ppm).] It is important to know whether the content is due to hardness-forming compounds alone or to other salts, and especially whether the chloride content exceeds about 50 mg/ L. The content of carbonic acid and of oxygen also is very significant. Microorganisms may accelerate or retard corrosion suspended solids such as sand usually are removed from industrial water before use the abrasion resistance of the zinc-iron alloy in coatings is helpful if suspended solids are present. 

The relatively high carbon content of iron produced in a blast furnace makes the metal hard but britde. It also has other impurities, like sulfur and phosphorus, that cause the recovered iron to be britde. The conversion of iron to steel is essentially a purification process in which impurities are removed by oxidation. This purification process is carried out in another kind of furnace at very high temperatures. All steel contains 0.02 to 1.5% carbon. In fact, steels are graded by their carbon content. Low-carbon steels typically contain 0.02 to 0.3% carbon. Medium -carbon steels typically contain 0.03 to 0.7% carbon. High-carbon steels contain 0.7 to 1.5% carbon. 

Chlorine and chlorine dioxide are other oxidizing agents that may be present in drinking water along with iron (III). Their interference can be removed by purging with nitrogen (for chlorine dioxide) or treatment with sodium oxalate (for chlorine) before analysis for iron (III). Nitrite can be decomposed with ammonium chloride in feebly acidic medium. 

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