Rensselaer Union, Volume 7, Number 44, Rensselaer, Jasper County, 22 July 1875 — Spontaneous Combustion. [ARTICLE]

Spontaneous Combustion.

Decay of inflammable substances, when exposed to the action of atmospheric oxygen, isin fact a very slow combustion, which by Liebig has been called Eremacausis. Thus, for example, a piece of wo<xl which, when burned, would produce a rise of temperature 1,000 deg. for say one minute, will, when slowly decaying during say 1,000 days, evolve the same 1,000 deg’ of heat; but being diffused over the length of time of 1,000 days will only evolve one deg. in twenty-four hours, or 1-440th of a degree per minute, a quantity of heat utterly inappreciable, as it is constantly lost in the surrounding atmosphere. Every housekeeper knows tliat •decayed wood is next to worthless for fuel, and the reason is simply that the heat obtained when sound wood combines rapidly th oxygen was lost during the slow .combustion_ or decay. / T , It is the same with coal when exposed to tlie access of the air. Under a shed it loses, according to the experiments of Varrenslrass, 25 per cent, of gas by oxidation and 10 per cent, of the heat-giving power, while when exposed without the protection of any shed, so much of the gaseous constituents are oxidized as to cause the coal to lose one-third of its original weight and more than one-half of its heating power. Of course during such oxidation heat is developed, but if the oxidation goes on slowly the heat is carried off as soon as it generates, and it is only when this carry - ing off of heat or cooling is prevented that the temperature may rise. The rise of temperature increases the tendency to oxidation; as nothing promotes more the activity of the oxygen in combining with combustible substances than heat, this increased oxidation again develops more heat, and thus, the action and reaction continuing, at last the flame bursts out; and this is what constitutes spontaneous combustion.

There are some substances very subject to such a combustion, for instance, vegetable and animal oils, especially drying oils. Thus linseed oil (the drying of which is a real oxidation) when poured upon a heap of sawdust or rags, placed so the air has access to the interior, will in a few hours break out in flames; if the air is excluded this will not take place—tree access of air or ventilation is necessary. When, however, the sawdust or rags are not placed in a single heap, but are diffused over the ground, so that the heat developed can diffuse itself by radiation, spontaneous combustion will be prevented; notwithstanding thefcontinued oxidation promoted by the free access of air, the mass will be kept, cool by the constant radiation of heat from the large surface exposed. This is an important hint in regard to the treatment of substances subject to spontaneous combustion; if it is impossible to spread them out so as to expose a large surface, and they have to be confined to a small space, as is the case in loading ships with such materials, ventilation must be prevented, as it is not practical to make it so active that the heat will be carried off more rapidly as it is developed by oxidation. In a blast-furnace the heat increases in proportion to the force of ventilation, and what takes place there at a high temperature takes place at a lower temperature in the incipient stage of spontaneous combustion.

The cases of spontaneous combustion of bituminous coal are so manifold and well authenticated that it is really a sign of utter ignorance of the facts taught by experience to deny it. We have had it in coal-yards as well as on board of ships; and where it took place a large mass of coal, say several thousand tons, was placed, not on the ground, but on a wooden floor, where air had access from below and a steady upward air-current took place through the interstices of the coal. Of course the coal lost its gaseous constituents by oxidation, as proved by the observation of Varrenstrass, referred to above. This oxidation, by necessity, developed heat, and,as the heat could notescape from the interior of the large mass, the temperature was constantly raised until, at last, combustion, at the usual high temperature, was established. Coal In mines, before shafts have been sunk, never ignites by spontaneous combustion; it is only when, by the sinking of shafts, ventilation has been established, that we hear of fires in coal mines; and if we can lock up the coal in a vessel as tightlv as it is in a mine before the shafts have been sunk the coal will be perfectly safe, and this none Of our antagonists dare deny.

It is a significant fact that no fires have occurred on board of coal-vessels transporting coal across the Atlantic, or on any voyage requiring no more time, but have often taken place on board of vessels going to the East Indies. California, and in general distances requiring more than forty days. Of course where the action of atmospheric oxygen on coal in large bulk can only raise the temperature of the interior ten degrees Fahr, per day it will in forty days, when starting at eighty degrees, be only 480 degrees; but evidently then the great danger commences, and it is clear how great an element time must be in this physical operation. — Manufacturer and Builder.

—William F. Frudner, night miller in St&mwitz & Shober's’flouring-mill, Minneapolis, while attending to his duties the other night, caught his clothing between the cogs to the spur wheel, ana he was slowly mangled. His body was not discovered until next morning, when it was found that he had been ground up by inches. His clothing was completelv stripped from his body, his arms crushed almost to a pulp, his right arm being torn from its socket, and his legs tangled and torn in the relentless wheels. In his desperate agony he had succeeded in taking off one shoe and hurling it into the wheels, which stopped their merciless grinding. He leaves a wife and three children. The orchards of this country are estimated to contain over 20,000,000 fruittrees. <