EXPLOSIBILITY OF COAL OILS. 333 



Both the artificial and natural petroleum in the crude state of a 

 tarry oil are found unfit to be burnt in lamps. After numerous at- 

 tempts to refine the crude petroleum by a second process of distilla- 

 tion, three remarkably different products were separately obtained. 

 Each one of these three substances having a different evaporative 

 or boiling point, like water and alcohol, they are readily separable 

 during one continued process of distillation, by gradually increasing 

 the heat beneath the still. 



The first product that comes over from the condenser is the volatile 

 spirits resembling ether and alcohol, called naphtha, benzole, benzine, 

 &c., which boil at a lower temperature than alcohol, (about 150° to 

 160° Fahrenheit's scale.) Naphtha evaporates as rapidly as ether, 

 producing similar lethean effects on breathing the vapor, and even 

 exceeds ether and alcohol in inflamtnability. 



It appears to be the common practice of the distillers of petroleum, 

 or coal tar, to keep the heat beneath the stills very low until this 

 naphtha has time to become evaporated at its boiling point of 160°, 

 and to flow from the condenser in a cr}'stalline stream into a cistern 

 arranged to receive it. When, by the test of a hydrometer, its 

 specific gravity is found to become increased to a certain degree by 

 containing some of the heavier coal oil, the str.eam from the con- 

 denser is diverted into another cistern designed for receiving the 

 second product of the distillation, being a heavier coal oil, commonly 

 known as "kerosene." 



The exact point where the naphtha becomes exhausted and the kero- 

 sene begins to flow is a nice question to be decided upon by the dis- 

 tiller. The extreme inflammability of the naphtha renders it unsafe 

 for burning in lamps; and it cannot be advantageously reduced to va- 

 por to be mixed with coal gas, because it does not form a permanent 

 gas; for the vapor, like that of alcohol, becomes condensed to a liquid 

 whenever it is cooled, as occurs on its passage through cold iron gas- 

 pipes under ground. The only available use of naphtha is for dissolv- 

 ing India-rubber, and for mixing w^ith painters' oil as a substitute for 

 spirits of turpentine. For these reasons naphtha is nearly worthless 

 for sale in the market; and as it constitutes ten or fifteen per cent, of 

 the petroleum used for distillation, there is a strong temptation to 

 the distillers to divert the current of naphtha into the kerosene oil- 

 cistern to gratify the cupidity of purchasers by thus affording the oil 

 at a low price. Thus both sellers and buyers are alike tempted to 

 disregard the danger resulting from mixing the naphtha with the kero- 

 sene oil. 



To gratify purchasers of coal oil by an extraordinary low price, it 

 has been stated that dealers have contracted for the waste naphtha 

 and residuary heavy coal oil or tar for preparing a mixture of about 

 the same specific gravity as kerosene oil, and resembling it in appear- 

 ance. The hydrometer is not, therefore, available for detecting this 

 spurious article, and there remains no other mode of ascertaining its 

 dangerous character than by actually testing its inflammability ex- 

 perimentally by the degree of heat indicated by a thermometer, at 

 which it will become kindled by the application of a lighted match, 



