Scientific Lectures. 225 



is submerged in a tank of water for the purpose of cooling it. When 

 the still has been filled with crude oil the lire is lighted beneath it, 

 and soon the oil begins to boil. The first products of distillation are 

 gases ; at ordinary temperature they pass through the coil and escape 

 without being condensed. 



Soon the vapors begin to condense in the worm, and a stream of oil 

 trickles from the far end of the coil into the receiving tank. The first 

 oils obtained have a gravity of about 95° B. ; as the distillation pro- 

 ceeds the product becomes heavier, 90° B., 85° B., 80° B., 75° B., 

 70° B., and so on. 



In most establishments it is customary to run the product into one 

 tank till the gravity reaches 65° B. to 59° B. ; the product known as 

 crude naphtha being subsequently separated by redistillation into (1) 

 gasoline, the lightest ; (2) naphtha ; (3) benzine. When the stream of 

 oil runs from the coil with a gravity from 65° to 59° B., it is diverted 

 into the kerosene tank and continues to run into this receiver till the 

 gravity reaches about 38° B., or until the color deepens to a yellow. 

 This second fraction is the burning oil or kerosene, and is subsequently 

 purified by sulphuric acid and alkali. 



After taking off the burning oil, the stream is directed to the paraffin 

 oil tanks, and continues to run there till nothing remains in the still 

 save coke. The last products have a gravity of about 25° B. 



The burning; oil is deodorized and bleached for market with sul- 

 phuric acid and alkali ; the crude naphtha is sold for from three to 

 five cents per gallon, and poured down the oil wells nominally to clean 

 them, but practically to be sold to the refiner again in the crude oil 

 at fourteen cents per gallon, or it is sold to be redistilled for gasoline, 

 refined naphtha and benzine. The well owners are many of them dis- 

 honest enough to pour the naphtha into the crude oil tank. This 

 adulteration now averages fifteen per cent. 



Some manufacturers, who pride themselves upon the superior quality 

 of their special brands of oil, separate certain portions of the distillate 

 and send them to market as unusually safe oils. 



The astral oil is probably the oil which runs from about 54° to 44° 

 B. ; in other words, the " heart " of the burning oil. As it does not 

 contain the lighter portions of the ordinary oil, its flashing point is 

 125° F., or 25° above the standard of safety, although its average 

 gravity is 49° B. The " mineral sperm " is a heavy oil, which probably 

 runs between 40° B. and 32° B., averaging 36° B. This is so heavy 

 and requires so high a temperature to volatilize it that it does not 



[Inst.] 1 5 



