106 ON THE EXPLOSIBILITY OF COAL OILS. 



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 in the oxygen 

 gas from the external atmospheric air. In this way only is an explosion 

 directly producible by saltpetre. But indirectly, as occurs in a burning 

 warehouse, a still more violent explosion than that of gunpowder is pro- 

 ducible 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 forcibly 

 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 ware- 

 house 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 carburetted 

 hydrogen gas was collected in another receiver inverted over water. The 

 two gaseous products were commingled in the proper combining pro- 

 portions, and introduced into a small tin tubular chamber, 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 gun- 

 powder. 



The dense smoke of burning floors, constituted of carburetted 

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

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

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

 them there. 



The explosiveness in this case manifestly originates from the 

 chemical combinations of the oxygen gas, set free by heating the salt- 

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

 pine wood, and not from any explosive property in the saltpetre itself. 

 For this special reason saltpetre stored by itself, without the proximity 

 of wooden floors beneath it, should not be considered in the class of a 

 hazardous risk for fire insurance, or intrinsically dangerous. 



As the dangerous inflammability of coal oil appeared to be ascribable 

 to the naphtha not separated therefrom, the following experiments 

 were made to ascertain the extent of the inflammable properties of pure 

 naphtha. 



