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Cool flame is a flame having maximal temperature below about . It is usually produced in a chemical reaction of a certain fuel-air mixture. Contrary to conventional flame, the reaction is not vigorous and releases very little heat, light and carbon dioxide. Cool flames are difficult to observe and are uncommon in everyday life, but they are responsible for engine knock – the undesirable, erratic, and noisy combustion of low-octane fuels in internal combustion engines.〔 ==History== Cool flames were accidentally discovered in the 1810s by Sir Humphry Davy, who noticed that certain types of flame did not burn his fingers or ignite a match. He also found that those unusual flames could change into conventional ones and that at certain compositions and temperatures, they did not require an external ignition source, such as a spark or hot material.〔, (Web version at NASA )〕〔H. Davy (1817) ("Some new experiments and observations on the combustion of gaseous mixtures, with an account of a method of preserving a continued light in mixtures of inflammable gases and air without flame," ) ''Philosophical Transactions of the Royal Society of London'', 107 : 77-86. On p. 79, Davy inserted a hot platinum wire into a mixture of air and diethyl ether vapor: "When the experiment in the slow combustion of ether is made in the dark, a pale phosphorescent light is perceived above the wire, which is most distinct when the wire ceases to be ignited. This appearance is connected with the formation of a peculiar acrid volatile substance possessed of acid properties."〕〔A number of other investigators subsequently also observed cold flames: * H. B. Miller (1826) ("On the production of acetic acid, in some original experiments with metallic and non-metallic substances over ether, alcohol, etc.," ) ''The Annals of Philosophy'', new series, 12 : 17-20. From page 19: "The tip of the glass rod held over the ether emits the blue flame from the whole of its surface ; acetic acid formed in abundance." * (Döbereiner) (1834) ("Sauerstoffabsorption des Platins" ) (Oxygen absorption by platinum), ''Annalen der Physik und Chemie'', 31 : 512. From page 512: ''"Eine andere nicht uninteressante Beobachtung von Döbereiner ist: dass Aether schon bei der Termperatur von 90° R. verbrennt, und zwar mit einer nur im Dunkeln wahrnehmbaren blassblauen Flamme, die nicht zündend wirkt, aber selbst so entzündbar ist, dass sie sich bei Annäherung einer brennenden Kerze augenblicklich in eine hochlodernde, hellleuchtende Flamme verwandelt."'' (Another not uninteresting observation of Döbereiner is that ether burns even at the temperature of 90° Réaumur with a pale blue flame that is perceptible only in the dark, which does not cause (to ) ignite, but itself is so flammable that on approach of a burning candle, it transforms instantly into a blazing, brightly glowing flame.) * Boutigny (1840) ("Phénomènes de la caléfaction" ), ''Comptes rendus'' … , 10 : 397-407. On page 400, Boutigny stated that when diethyl ether was added dropwise to a red-hot platinum crucible, an irritating, acidic vapor was produced. ''" … il est bien à présumer qu'il s'opère là une combustion lente, … "'' ( … it is well to presume that a slow combustion is taking place there … ) * Pierre Hippolyte Boutigny, ''Études sur les corps à l'état spheroidal: Nouvelle branche de physique'' (on bodies in a spheroidal state: a new branch of physics ), 3rd ed. (Paris, France: Victor Masson, 1857), pp. 165-166. (On page 166 ), Boutigny noted that when he poured some diethyl ether into a hot crucible: ''"Dans une obscurité profonde, on aperçoit, à toutes les phases de l'expérience, une flamme d'un bleu clair peu apparent, qui ondule dans le creuset dont elle remplit toute la capacité. Cette flamme rare et transparente est le signe d'une métamorphose profonde qui subit l'éther ; elle est caractérisée par le dégagement d'une vapeur dont l'odeur vive et pénétrante irrite fortement la muquese nasale et les conjonctives."'' (In deep darkness, one perceives, at all stages of the experiment, a flame of an inconspicuous light blue, which ripples in the crucible which it fills completely. This rare and transparent flame is a sign of a profound metamorphosis that the ether undergoes ; it is characterized by the release of a vapor whose sharp and penetrating odor strongly irritates the nasal mucosa and conjunctiva (the eyes ).) * W.H. Perkin (1882) ("Some observations on the luminous incomplete combustion of ether and other organic bodies," ) ''Journal of the Chemical Society'', 41 : 363-367.〕 Harry Julius Emeléus was the first to record their emission spectra, and in 1929 he coined the term "cold flame".〔Harry Julius Emeléus (1929) "The light emission from the phosphorescent flames of ether, acetaldehyde, propaldehyde, and hexane," ''Journal of the Chemical Society (Resumed)'', pp. 1733-1739.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「cool flame」の詳細全文を読む スポンサード リンク
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