EXPLOSIBILITY OF COAL OILS 339 



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 as- 

 cribable to the naphtha not separated therefrom, the following experi- 

 ments were made to ascertain the extent of the inflammable properties 

 of pure naphtha. 



Finding that the liquid naphtha evolved sufficient vapors at the 

 ordinary temperature of the atmosphere to become instantaneously 

 kindled into flashing flames, the cup containing it was immersed in a 

 freezing mixture of snow and salt to reduce the temperature to the 

 zero of Fahrenheit's scale. At this low temperature the naphtha 

 appeared to blaze with equal violence. Then a quantity of snow was 

 mixed with the liquid naphtha and thoroughly stirred, for still further 

 reducing the temperature. Even at this extreme degree of cold the 

 naphtha continued to flame so furiously that it was necessarily thrown 

 from the cup, upon the ice covering the ground where the experiment 

 was made, in the open air, whilst the thermometer indicated an at- 

 mospheric temperature of 19° below the freezing point. The naphtha 

 still continuing to burn upon the surface of the ice, a covering of 

 snow was thrown over it to extinguish the flame. Through this 

 covering of white snow the bright flames still continued to shoot up, 

 presenting to view the extraordinary spectacle of burning snow. 



On repeating similar experiments on the comparative combustibility 

 of spirits of wine or alcohol, camphene, and burning fluid, they did 

 not emit sufficient gaseous vapors at the freezing point, or 32° to 

 become kindled into flame, when burning matches were plunged 

 therein, but with a little increase of temperature they all became 

 kindled. 



The preceding experiments seem to exhibit impressively the ex- 

 traordinary inflammability of naphtha, arising from the facility with 

 i which it emits gaseous vapors. Susceptible of being readily kindled 

 ' into flames, even through a mantle of snow, naphtha, like ether, emits 

 ' gaseous vapor, which, with surprising facility, pervades the air; and 

 ; the odor of it being rather pleasant than oflensive, like that of art - 

 ficial coal gas, the utmost caution is requisite to prevent not only 

 ' unexpected explosions; but also the almost unextinguishable violence 

 ' of its conflagration, for practically the application of water does not 

 I subdue the conflagration of naphtha in quantity, and only the exclu- 

 ' sion of atmospheric air appears to quench the fury of its flames. To 

 prevent the escape of the gas through the porous wooden staves, it 

 has been found necessary to coat the inside of the barrels with a 

 solution of glue. 



The insidious nature of the gaseous vapor of naphtha is therefore 

 its most dangerous quality, for when stored in barrels in a warehouse, 

 with the bung holes of the barrels open, sufficient vapor escapes into 

 the air of a close apartment to produce a violent explosive action on 

 introducing a lighted candle. In this way, notwithstanding tlie pre- 

 cautious used at the distilleries of coal oils, several of them have been 



