PURIFICATION OF PETEOLEAN OILS. 159 



PURIFICATION OF PETROLEAN OILS. 



An almost colourless naphtha arises from the earth at Baku, on the 

 border of the Caspian Sea, accompanied by hydrocarbon vapours, which 

 are collected and used for heating and lighting. It is also used in lamps 

 in its natural state. A single distillation renders it quite pure. From 

 the presence of paraffin the Rangoon petroleum is nearly of the consistence 

 of butter at the ordinary temperature. It has been treated with sulphuric 

 acid and the alkalies in the manner recommended for coal oils. The 

 parathne, which was first discovered by Mr. Faraday, is also treated with 

 the acids, and then submitted to pressure. Much of the Persian oil is 

 colourless, and is consumed in lamps without purification. 



The petroleum of South America and the West India Islands often 

 contain much sulphur, and their odour is very offensive. The petro- 

 leums of volcanic districts were much more offensive than those of un- 

 disturbed localities. Boiling mud with steam issues from the earth on 

 the shores of Trinidad, and raises itself into conical mounds, sometimes 

 fifty feet high. The petroleum at those places has an intolerable odour, 

 and contains sulphuretted hydrogen. Gold is i mmediately tarnished by 

 the gases of these sulphurous distric s. All these natural hydrocarbon 

 oils require active treatment to render them unobjectionable for domestic 

 purposes. The alternate use of acids and alkalies have been found the 

 most effectual in their purification. 



The petroleums of the United States, of which great quantities 

 are now obtained, differ much in their densities of proofs. Some of 

 the wells in Venango county, Pennsylvania, afford oils of a specific 

 gravity O800. In other parts of the oil region the petroleums have 

 densities of 0*850, and even 0.900. Indeed these heavy semi-liquid 

 hydro-carbon compounds sometimes pass into compact bitumen, an 

 example of which may be seen in Jackson county, Kentucky, and also 

 at other places. 



These deposits of solid bitumen have probably been produced by the 

 evaporation of the higher hydro-carbons, and by the oxydation of those 

 beds which now appear like the sites of ancient lakes. They are quite 

 different in their origin and characters from the injected masses of solid 

 asphalte discovered in Richie county, Virginia, and in Albert county, in 

 the province of New Brunswick. 



From the great difference in the densities of these petroleums, there 

 is a great difference in regard to their value and their treatment in the 

 process of purification. Of the lighter oils, ninety per cent, of pure oil 

 for illuminating purposes may be obtained ; but of the more dense varie- 

 ties, and those which contain much tarry matter, not more than forty or 

 fifty per cent, of lamp oil is at present produced. The result has been 

 the same as that in the manufacture of coal oils. Large quantities of 

 the heavy oils and impure paraffin accumulate in the distilleries, and 



