548 PETROLEUM 



means of a strap and pulley from a small steam-engino of about 1 or 2 horse-power. 

 When the boring is finished, the same arrangement is used to work the oil-pump. 

 The use of the intermediate beam and driving-belt allows the boiler, which is 

 usually of the common agricultural or portable form, to be kept at a safe distance 

 from the stream of inflammable gas, accompanying the oil and water brought up. 

 The mixed fluid lifted by the pump is received in large open vats, in "which the 

 separation takes place ; the water being allowed to run off by a waste-pipe below, 

 while the oil accumulates until a sufficient quantity has been collected for barrelling. 

 The standard measure for petroleum is the barrel of 40 American or old wine-gallons, 

 equal in -weight to about 3 cwts. 



From what has already been stated, it will be easily understood that petroleum 

 varies considerably in composition and density, according to whether it be derived 

 from shallow or deep wells, the former giving the darkest and heaviest products. 

 The following are some of the chief properties of different American oils, according 

 to Gesner : Pennsylvanian petroleum is dark coloured, with a peculiar greenish 

 lustre or fluorescence ; by reflected light, the specific gravity varies from 0'782 to 

 0'820. When refined, the distillate yields from 75 to 85 per cent, of illuminating oil, 

 giving off inflammable vapours at a temperature of from 110 to 116 F. The heavy 

 oils produced in the distillation yield paraffin, or may be used for lubricating. The 

 specific gravity of heavy natural or lubricating oil from Pennsylvania, is from O'SOO 

 to 0-860. 



Oil from Mecca, Ohio, which remains fluid at very low temperatures, has the 

 specific gravity 0'890 to 0'910. The Canadian or Enniskillen petroleum is dark 

 coloured, and has a peculiar and very offensive smell, but yields a larger quantity of 

 burning oils than the Pennsylvanian ; its specific gravity is from 0'860 to 0'880 ; that 

 of the rectified burning-oil is 0-838. A sample of Californian petroleum, of the 

 specific gravity 0-927, yielded the following products when refined : 



Illuminating oil 38 per cent. 



Lubricating oil . . . . . . . 48 



Pitch 10 



Water 4 



Another sample from California lost from 10 to 15 degrees by volume, yielding, on 



rectification : 



Per cent. 



Light oils ......5 

 Burning oil ........ SO 



Light machine-oil . 20 



Heavy oil and paraffin 25 



The bitumen of the gum-bed of Enniskillen yields 50 per cent, of volatile products 

 by distillation ; and the Rangoon tar contains about 10 or 11 per cent, of paraffin. 



The refining of petroleum has already been noticed under NAPHTHA. The following 

 is a sketch of the operation as performed at a small refinery at Oil Springs, Canada 

 West. The crude oil, purchased from the proprietors of the -wells, is stored in large 

 underground tanks. For refining, wrought-iron stills are employed, having a capacity 

 of 40 barrels, or 1,600 gallons; they are flat-bottomed, and are provided with man- 

 holes, through which the black pitchy residue is removed. When the charge is intro- 

 duced the still is closed, and the distillation is effected by a fire placed beneath. The 

 charge takes about a week to work off; the distillate is collected in large wooden tubs, 

 a small quantity of a thick greenish substance separating from it, which is returned 

 to the still. The pitchy residue in the still is not subjected to any further treatment, 

 but forms part of the fuel used in the next distillation. The liquid collected is mixed 

 with from 5 to 10 per cent, of sulphuric acid, and agitated by rotatory paddles at a 

 steam-heat, for the purpose of bleaching it. After this is done, the bleached oil is 

 washed with water, the last faint traces of acid are neutralised with caustic potash, and 

 it is finally deodorised with ammonia. When freshly prepared, the refined oil is without 

 colour or smell ; and when seen in large quantity, exhibits the extraordinary blue, or 

 fluorescent rays of Professor Stokes in a striking manner. The loss in distillation is 

 about 30 per cent. ; the refined oil is packed in 40-gallon barrels made of oak, which, 

 before they are used, are lined with an elastic cement resembling vulcanised india- 

 rubber, the principal ingredients of which are glue and white lead, in order to prevent 

 leakage through the joints of the staves. 



The gigantic dimensions of the American petroleum trade may best be represented 

 by the following statistics given in evidence, before a Select Committee of the House of 

 Lords, in 1872 : 







