338 EXPLOSIBILITY OF COAL OILS. 



appears to have been lost sight of in the numerous discussions of the 

 questions of "the explosibility of saltpetre," which have been pub- 

 lished, and in the experiments that have been made to ^olve practi- 

 cally this unsettled question. These experiments have shown that 

 where fragments of charcoal not finely pulverized, such as are pro- 

 duced from burning wood, and from cloth commonly used for bag- 

 ging, are thrown upon heated saltpetre, a prolonged vivid combustion 

 has ensued, termed deflagration, in contradistinction to explosion, the 

 contact of the two substances being confined to the surfaces of the 

 solid masses. To produce explosive action with saltpetre and char- 

 coal when ignited, it has therefore been found necessary to pulverize 

 both substances very finely and then to commingle them, atom to atom, 

 artificially, with the utmost care, as is practically accomplished in the 

 manufacture of gunpowder. When thus prepared, the saltpetre sets 

 free sufficient pure oxygen to be chemically combined, atom to atom, 

 with the charcoal or carbon in the confined chamber of a cannon, 

 independently of a supply of the oxygen gas from the external 

 atmospheric air. In this way only is an explosion directly produci- 

 ble by saltpetre. But indirectly, as occurs in a burning warehouse, 

 a still more violent explosion than that of gunpowder is producible 

 by simply mixing together the gaseous products of saltpetre and 

 burning wood, as the following experiment, made in the laboratory of 

 Brown University, with the co-operation of Professor Hill, will forci- 

 bly demonstrate. 



Some saltpetre was put into a retort, and subjected to the heat of 

 a furnace, to represent the action of the intense heat of a burning 

 warehouse on saltpetre stowed therein. The gas evolved from the 

 saltpetre was collected in a glass receiver. Some fine sawdust was put 

 into another retort, similarly heated in a furnace, and the rising car- 

 buretted hydrogen gas was collected in another receiver inverted over 

 water. The two gaseous products were commingled in the proper 

 combining proportions, and introduced into a small tin tubular cham- 

 ber, with a cover loosely fitted on its top, and a small hole pierced in 

 its side, to which a lighted match was applied. An explosion ensued 

 so violent and rapid that the top of the circular cover was burst off 

 from its soldered edge before it was lifted up, and the hoop of it split 

 open and thrown to a distance with a deafening report. 



After witnessing the violent and stunning explosion thus produced 

 by a minute quantity of the mixed gases of pine wood and saltpetre, 

 the professor remarked that a room full of such an explosive mixture 

 might produce the terrific effect of the explosion of a magazine of 

 gunpowder. 



The dense smoke of burning floors, constituted of carburetted 

 hydrogen, and the puro oxygen evolved by the heat of them from 

 the saltpetre, might ascend into some adjacent room and remain com- 

 mingled there, ready to explode by the first flash of flame which 

 might reach them there. 



The explosiveness in this case manifestly originates from the chemi- 

 cal combinations of the oxygen gas, set free by heating the saltpetre. 

 with the carburetted hydrogen gas, set free by the heating of the 



