CONCERNING KEROSENE. 253 



about 1,200 barrels each, beneath which fires may be kindled, and 

 urged by a strong draught until a red-heat is attained. 



Petroleum consists of a great many different fluids, which range 

 in volatility from the boiling-point of ether to nearly a red-heat. Such 

 being the case, as soon as the oil is heated at all, the most volatile 

 products begin to come over, at first colorless as water, but very 

 gradually assuming a yellow tinge until the most dense distillate com- 

 ing over at the last is quite dark brown in color, so that, if all the dis- 

 tillate were allowed to run into a tank together, it would not look very 

 differently from the original petroleum. In the ordinary process of 

 refining petroleum, the distillate is divided into three portions. The 

 first is the lightest, colorless portion, nearly as volatile as ether, and is 

 called crude naphtha, or "benzine." Like the crude petroleum, this 

 crude naphtha may be distilled and divided into gasolene, A, B, and C 

 naphtha, which are used in gas-machines, for mixing paints, and other 

 similar purposes, sometimes also for burning in lamps and stoves. 



The middle portion of the distillate, which is neither very light nor 

 very heavy, and having but little color, is the crude illuminating-oil, 

 or kerosene. As it runs from the still it has a very offensive odor, due 

 to the decomposition of certain portions of the petroleum at the high 

 temperature reached in the still. To remove the offensive compounds, 

 the oil is first agitated with about five per cent of strong oil of vitriol. 

 This combines with the offensive oils, forming a black, tarry residue 

 that falls to the bottom of the tank as soon as the oil is brought to 

 rest. This mixture of acid and oil is called " sludge," and is used in 

 large quantities in the manufacture of commercial fertilizers. After 

 the acid is drawn off and the oil washed with water, it is again washed 

 with a strong solution of caustic soda, which removes the excess of 

 sulphuric acid, and also some peculiar acid compounds that exist in 

 the oil. The oil, after another washing with water, is nearly colorless, 

 with the peculiar balsamic odor of kerosene, and possesses the slight 

 opalescence peculiar to these oils. As usually prepared, they belong 

 to the class known as " high-test " kerosenes, and consist almost en- 

 tirely of oils that exist in the petroleum already formed, being merely 

 separated from the lightest and heaviest portions. Such oils are called 

 the eclucts of the petroleum. 



The heaviest portions of the distillate contain paraffine, and are 

 called paraffine-oils. They also are mainly educts of the original oil ; 

 they, however, contain a much larger proportion than the kerosene of 

 the products of the decomposition of the oil. A tarry residue remains 

 in the still, called " residuum." 



In other establishments the naphtha and illuminating oil are dis- 

 tilled from the petroleum, and the dense oil remaining in the still, 

 called "reduced petroleum," is draM r n out and used for lubrication. 

 A large part of this dense oil from which the naphtha and illuminat- 

 ing oil have been removed is " cracked," or destructively distilled, by 



