Spontaneous Combustion is a phenomenon that occasionally manifests itself in mineral and organic substances. For some facts connected with the spontaneous ignition of mineral substances, see PYROPHORUS. Ordinary charcoal does not undergo combustion in air below a temperature of 1000°, but in some states, especially when impregnated with oil, it is liable spontaneously to acquire a temperature which may lead to unexpected combustion. There have been many instances of the spontaneous ignition of coals containing iron Pyrites (q.v.) when moistened with water. The pyrites which most readily give rise to spontaneous combustion are those in which the protosulphide is associated with the bisulphide of iron; and these occur among the Yorkshire coals and in some kinds of South Wales coal. Sulphur has no tendency to spontaneous combustion, but Dr Taylor refers to an instance that came to his own knowledge, in which there was reason to believe that the vapour of bisulphide of carbon in an india-rubber factory was ignited by solar heat traversing glass. Phosphorus, when in a dry state, has a great tendency to ignite spontaneously, and it has been observed to melt and take fire (when touched) in a room in which the temperature was under 70°. The ordinary lucifer-match composition is luminous in the dark in warm summer nights, which shows that oxidation, and therefore a process of heating, is going on. Hence large quantities of these matches kept in contact may produce a heat sufficient for their ignition. 'I have seen them ignite,' says Dr Taylor, 'as a result of exposure to the sun's rays for the purpose of drying.'
In organic substances, apart from the accidents that may result from the admixture of strong nitric or sulphuric acid with wool, straw, or certain essential oils, and which, if they occur, are immediate and obvious, there are many cases in which, 'without contact with any energetical chemical compounds, certain substances—such as hay, cotton and woody fibre generally, including tow, flax, hemp, jute, rags, leaves, spent tan, cocoa-nut fibre, straw in manure-leaps, &c.—when stacked in large quantities in a damp state, undergo a process of heating from simple oxidation (crematisation) or fermentation, and after a time may pass into a state of spontaneous combustion' (Taylor). Cotton, woollen articles, hemp, tow, and flax impregnated with oil, when collected in large quantity, are specially liable to ignite spontaneously; and the accumulation of cotton-waste, used in wiping lamps and the oiled surfaces of machinery, has more than once given rise to accidents, and led to unfounded charges of incendiarism. Dr Taylor relates a case in which a fire took place in a shop 'by reason of a quantity of oil having been spilled on dry sawdust.' According to Chevallier, vegetables boiled in oil furnish a residue which is liable to spontaneous ignition. The great fire at London Bridge in 1861 was referred to the spontaneous combustion of jute in its ordinary state; but Dr Taylor remarks that this is wholly incredible, and from experiments which he made for the defendants in the case of Hepburn v. Lordan (1865), and on other grounds, he holds that there is even no evidence of moist jute undergoing spontaneous combustion. Dry wood is supposed by Chevallier and some other chemists to have the property of igniting spontaneously. Deal which has been dried by contact or contiguity with flues or pipes conveying hot water or steam at 212° is supposed to be in a condition for bursting into flame when air gets access to it; and the destruction of the Houses of Parliament, and many other great fires, have been ascribed to this cause; but it appears that some amount of charring is necessary, and that on slight cooling a considerable quantity of oxygen is absorbed from the air, which induces a sufficient rise of temperature to set up spontaneous combustion. In a case recorded in the Annales d'Hygiène for 1841, MM. Chevallier, Ollivier, and Devergie drew the conclusion that a barn had caught fire from the spontaneous combustion of damp oats which were stored in it. No such cases are known to have occurred in Great Britain. See also FIRE, p. 634; and GUN-COTTON, p. 468.
Spontaneous combustion of the human body is supposed to have occurred in a number of recorded cases, of which one of the earliest was that of Mme. Millet at Rheims in 1725, and one of the most notable that of a man found burning in bed in 1847 (Gazette Médicale, 4th September 1847). Some of the alleged cases have been traced to wilful burning after murder; some are plainly incredible; the remainder, with the exception of the 1847 case, which remains unexplained, can all be traced to the destruction of the bodies of intoxicated brandy-drinkers, near an open fire in winter, with no one present and no evidence forthcoming as to the time occupied in the combustion, or as to the circumstances, other than intoxication, preceding the combustion. Liebig discusses the subject in his Letters on Chemistry, and concludes that, while a fat dead body charged with alcohol may perhaps burn, a living body, in which the blood is circulating, cannot take fire under any circumstances.
For further details the reader is referred to Graham's 'Report on the Cause of the Fire in the Amazon,' in the Quarterly Journal of the Chemical Society, vol. v. p. 34; to the article 'Combustion' in Watts's Dictionary of Chemistry, vol. i.; and to the elaborate chapter on this subject in Taylor's Principles and Practice of Medical Jurisprudence. For spontaneous combustion in the human body, see the article thereon in the Medical Encyclopædias; the preface to Dickens's Bleak House; Liebig's Letters on Chemistry; Dupuytren's Leçons Orales; and Taylor's Medical Jurisprudence.