161 



with it much of the remaining impurities, and can be drawn 

 off by a stop-cock at the bottom. Then the oil is agitated 

 with pure water to wash out the remains of the acid. Then 

 a strong lye of potash or soda is introduced, and the stir- 

 ring repeated, which is followed by a second washing with 

 water. The oil is now ready for its second distillation. 



This is conducted in a set of stills similar to the first. 

 The heat is kept at a low point at first, not higher than 

 120°, until all the more volatile oil is driven over. This is 

 collected by itself, and is now known as naphtha. It is as in- 

 flammable and volatile as turpentine, and has since the great 

 increase in price of this latter material, been largely used 

 in its place for paints, varnishes, &c. For these purposes it 

 is well adapted, except that its odor is to many more offens- 

 ive than that of turpentine. It is also extensively used as 

 a solvent for India rubber in the manufacture of rubber 

 cloths and other fabrics. 



When the naphtha has been entirely expelled, the heat is 

 gradually raised, and an oil heavier, less limpid and odor- 

 ous is driven over. The specific gravity of the distilled 

 oil becomes greater and greater with the increasing heat. 

 When the specific gravity has reached 0.820, the oil beyond 

 this is not considered suitable for purposes of illumination, 

 and is collected separately, and used for lubricating. The 

 quantity of merchantable illuminating oil varies with dif- 

 ferent varieties of the crude from thirty per cent up to 

 eighty or ninety per cent. 



The lubricating oil is driven off at a higher temperature, 

 is more viscid, and darker in color. The heaviest of this 

 oil is used for extracting paraffine, which collects in beau- 

 tiful crystals when cooled down to a very low temperature. 

 Lastly, there remains a black tarry matter, mingled with 

 the chemicals used in the purification, which has not as yet 

 been utilized. We may enumerate, then, four useful pro- 

 ducts from the distillation of crude Petroleum. 



1. JVaphtha, extracted at a temperature below 120°, a thin, 



