Charcoal, oxygen oxidation

Dichlorine oxide Carbon, or Oxidisable materials Fluorine Non-metals Hydrogen peroxide Carbon Iodine heptafluoride Carbon Iodine(V) oxide Non-metals Nitrogen oxide Non-metals Nitrogen trifluoride Charcoal Oxygen difluoride Non-metals Oxygen (Liquid) Charcoal Ozone Charcoal, Potassium iodide... 

A particularly useful preparation of DHA, described by Ohmori and Takagi, uses oxygen oxidation over a charcoal catalyst (6). The use of oxygen and charcoal to convert AA to DHA is a well-known reaction that has been used in AA assays for many years. The oxidation can be made in ethanol, methanol, water, or various mixtures of these solvents. We carry out this procedure as follows ... 

The best approach to the structure of monomeric DHA was through H NMR and NMR studies. On the basis of H NMR, DHA was proposed to exist in aqueous solution as a bicyclic hydrated species, that is, 3,6-anhydro-L-xt/Zo-hexulono-l,4-lactone hydrate (53). We have made further studies on this structure using DHA prepared by oxygen oxidation in ethanol, or methanol or water using charcoal as a catalyst. The method is described earlier in this chapter. 

Lead was one of the first metals to be extracted as it melts at 327°C and is reduced by carbon just below 800°C. The main ore is galena (PbS), and may be readily smelted in a charcoal or dry wood furnace. At the top of the furnace where there is an abundant supply of oxygen (oxidizing), the sulfide is roasted to the oxide ... 

Electron-spin resonance has been measured at 9400 and 51.7 Me. for a variety of charcoals heated to various temperatures. A very sharp resonance line has been observed by proper heat treatment and subsequent evacuation of the charcoal. Oxygen and nitric oxide adsorption at room temperature decrease the absorption intensity and widen the absorption band. Nitrogen and hydrogen have no effect at room temperature on the electron-spin resonance of the charcoal. 

The Kestner-Johnson dissolver is widely used for the preparation of silver nitrate (11). In this process, silver bars are dissolved in 45% nitric acid in a pure oxygen atmosphere. Any nitric oxide, NO, produced is oxidized to nitrogen dioxide, NO2, which in turn reacts with water to form more nitric acid and nitric oxide. The nitric acid is then passed over a bed of granulated silver in the presence of oxygen. Most of the acid reacts. The resulting solution contains silver at ca 840 g/L (12). This solution can be further purified using charcoal (13), alumina (14), and ultraviolet radiation (15). 

Nitric oxide combines readily with atmospheric oxygen at ambient temperature to produce brown fumes of pungent nitrogen dioxide, and in the presence of charcoal with chlorine to form nitrosyl chloride ... 

Although this chemistry is complex, the basic process is reduction of iron oxide by carbon in an atmosphere depleted of oxygen. Archaeologists have found ancient smelters in Africa (in what is now Tanzania) that exploited this chemistry to produce iron in prehistoric times. Early African peoples lined a hole with a fuel of termite residues and added iron ore. Chamed reeds and charcoal provided the reducing substance. Finally, a chimney of mud was added. When this furnace was fired, a pool of iron collected in the bottom. 

Leblanc wrestled with the problem for five years between 1784 and 1789. Then finally, somehow, someway, he stumbled on the solution. Ancient ironmakers had used carbon in the form of charcoal when hot, the carbon is highly reactive and wrests the oxygen from iron oxide ores. As Leblanc heated his sodium sulfate with charcoal, he added a key new ingredient—common limestone (chalk)—as his source of C03. Almost miraculously, the transformation took place ... 

Some chemical processes use energy directly to drive the transformation. For example, the conversion of iron ore, iron oxide, to iron metal requires chemical energy to remove the oxygen atoms. In early times the iron ore was heated with charcoal in more recent times it is heated with refined coal (coke), but in both cases the result is conversion of coal or wood into carbon monoxide, which is toxic but can be burned to carbon dioxide to generate needed heat. There is now interest in devising processes that do not use carbon in this way, but use electrical energy to avoid the production of carbon oxides. 

Extractable matter should be removed by extraction with organic solvents, e.g., xylene. This is especially important for carbon blacks (25), Oxidized carbon may contain small amounts of oxalic acid. King (33, 34) found 0.002 meq/gm of oxalic acid in oxygen-treated sugar charcoal. More severe is the contamination of the surface with adsorbed gases, mainly carbon dioxide and water. Activated carbon with narrow pores may contain considerable amounts of carbon dioxide (28). The best... 

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