Hydrogen slow combustion

Methyl ethyl ketone is unique, in that long and irreproducible induction periods were observed on occasion, reaction ensued only after 7 hours and then was completed within 10 minutes. During the long induction period the only detectable product was methanol. No convincing reason can be advanced to account for this anomalous behavior. The virtual absence of ethylene from the products of the low temperature slow combustion of methyl ethyl ketone strongly suggests that the low-temperature mechanism proceeds almost exclusively by further oxidation of the radicals produced by hydrogen abstraction from the parent ketone. 

Figure 6 shows the variation of peroxide concentration in methyl ethyl ketone slow combustion, and similar results, but with no peracid formed, have been found for acetone and diethyl ketone. The concentrations of the organic peroxy compounds run parallel to the rate of reaction, but the hydrogen peroxide concentration increases to a steady value. There thus seems little doubt that the degenerate branching intermediates at low temperatures are the alkyl hydroperoxides, and with methyl ethyl ketone, peracetic acid also. The tvfo types of cool flames given by methyl ethyl ketone may arise from the twin branching intermediates (1) observed in its combustion. 

The Slow Combustion of Hydrogen.—Owing partly to its familiarity, and partly to the ease with which it can be obtained in a highly pure condition, electrolytic gas has been studied by many investigators from the point of view of slow combustion. 

The slow combustion of this compound [95] also possesses a region of negative temperature coefficient between 320 and 360 °C and it very readily gives rise to cool flames [45]. The major products are aldehydes and acids, propionic acid and propionaldehyde predominating at high temperatures. At low temperatures considerable amounts of hydrogen peroxide are formed. 

The slow combustion of methylene chloride is a degenerately branched chain reaction it proceeds by a mechanism similar to that involved in the pyrolysis of the same compound which takes place at a slightly higher temperature [153]. The primary chains are the same and several of the chlorinated hydrocarbon minor products are identical. Oxygen is only involved in the conversion of the intermediate dichloroethylene to the final products hydrogen chloride and carbon monoxide. 

Notwithstanding the obstacles, however, some absorption studies of combustion processes have been made. Molecular intermediates, such as aldehydes and acids, have been identified in the slow combustion of propane . Hydroxyl radicals can be observed in the absorption spectra of several flames . The greatest success in the application of absorption spectroscopy to flame studies has been in investigations of diffusion flames. Wolfhard and Parker studied the diffusion flames in oxygen of hydrogen, ammonia, hydrocarbons and carbon monoxide. In every case they were able to observe absorption by hydroxyl radicals, and they observed also the absorption of NH in the ammonia flame (NH2 appeared in emission only). Molecular oxygen, and in suitable cases the reactants, could be detected by their absorption spectra, so that a clear picture of the structure of the diffusion flame... 

Respiration is only a slow combustion of carbon and hydrogen, similar in every way to that which takes place in a lamp or lighted candle and, from this viewpoint, breathing animals are actual combustible bodies that are burning and wasting away. 

The most severe hazard caused by hydrogen release is that it will be released, sooner or later according to the conservative assumptions made in severe accident studies, into the primary containment atmosphere where it may cause, in the presence of air, explosions or relatively slow combustion. In both cases, the internal pressure in the primary containment will increase and its integrity will be endangered. The containment safety margins against internal pressure are, however, normally high. ... 

Dalton did not accept Gay-Lussac s law, since it did not agree with his own experiments. In his notebook on 6 October 1805 he wrote It appears from sundry expts. that hyd. fired with oxigen gives 100 ox. for 190 hyd. — it seems too that when the combustion is very rapid there is some trace of oxig. left in the hydrogen. In slow combustion it should seem as if 100 ox. required 200 hyd. In his later criticism of Gay-Lussac s results he says ... 

The heat of combustion of fast coke, AHf, takes into account both CO and CO2 formation as well as the combustion of the hydrogen in the coke. The heat of combustion of the slow coke is given by... 

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