SHALES AND MINERAL OILS 773 



makers reckon steam as an indispensable adjunct in the distillation of crude oils. 

 Experience has proved Torbanehill mineral to give 120 gallons per ton -with steam; 

 and only 90 gallons without it. Shale yields 40 gallons with steam, and 30 gallons 

 without it. The difference in yield of finished products is 75 to 76 per cent, of tho 

 two crude oils respectively manufactured. In vertical crude the proportion of mineral 

 spirits and burning oil is less than in horizontal, but 3 per cent, more paraffin is 

 obtained. 



Purification of the Crude Oil. The crude oil issues as vapour into the condensers ; 

 it pours out at their extremity, as a mixed liquid of oil and water, into the separator. 

 This is a wooden cylinder, 4 feet high and 3 feet broad. Through this barrel an 

 iron syphon passes ; this emerges at the side, a few inches from the top, and termi- 

 nates about 8 inches from the bottom. The ammonia-water soon sinks under the 

 crude oil, with which it is mixed on entering, by its higher specific gravity ; whence 

 it is drawn off by the above syphon. Almost at the top of the separator is another 

 aperture, to serve as an educt for the crude oil. 



The ammonia-water is next converted by the usual manufacturing methods of stills 

 and evaporating-pans, into sulphate of ammonia. Some shales yield 8 to 10 Ibs. of 

 the sulphate per ton, whilst others give as much as 16 Ibs. to the ton. 



The crude oil is now transferred to the refinery by one of the series of underground 

 pipes, in connection with the centrifugal pump worked by steam which now forms so 

 integral a part in the economy of the establishment. The oil refinery, with tanks in 

 which centrifugal revolving-stirrers, often only 2 feet in diameter, move by steam in 

 iron vessels 10 feet in diameter, and agitate tho oil with either sulphuric acid or soda. 

 About 200 revolutions are made in a minute, and so a quarter-of-an-hour's agitation 

 of the oil serves, instead of the night's work of early refining. There are also settling 

 tanks, and a series of iron-pipes, which connects the oil with the stills outside, intro- 

 duces the vitriol and soda used in purifying, or removes tho vitriol and soda tars from 

 the treated oils ; all are subordinated to the main steam-pump. Indeed, throughout 

 the varied processes the steam-engine as much as possible supplants mere manual 

 toil ; intelligent superintendence being only required from the few artizans on the 

 establishment. The paraffin-house is usually distinct from the oil-refinery; it may 

 contain only presses for making ' scales,' or the varied apparatus for the manufacture 

 of refined paraffin. In either case, if the establishment is large it is associated with 

 cooling-drums and an ice-machine, all of which, along with the presses, are worked 

 by steam-power. In many large refineries the mineral spirits are refined in a sepa- 

 rate building in connection with the paraffin-house. This is for greater safety from 

 fire, which is sedulously guarded against by the adoption of iron doors, roofing, pro- 

 hibition of smoking, use of covered lights, and such like appliances, throughout the 

 entire establishment. 



The following is a diagrammatic sketch of the various distillations of crude oil in its 

 manufacture into burning oil : 



CRUDE OIL FROM SEPARATOR. 



FIRST DISTILLATION. 



Once-run oil. Coke in Bottom of Still. 



20 lower in sp. gr. than crude. 7 per cent, of oil converted into this, used 



as fuel, or drawn off as tar for patent 

 fuel. 



First Washing. Second Washing. 



5 per cent, brown vitriol, sp. gr. 1-745. 4 per cent, caustic soda, sp. gr. T300. 

 May stand over a night in tank. Stirred for an hour. 



SECOND DISTILLATION. 



Third Washing. Fourth Washing. 



1 per cent, ordinary commercial vitriol. 2 per cent, caustic soda, sp. gr. 1-300. 



THIRD DISTILLATION. 



Fifth Washing. Sixth Washing. 



% per cent, ordinary commercial vitriol. ^ per cent, caustic soda, sp. gr. T300. 



Product. Ordinary burning oil. 



FOtTETH DISTILLATION. 



Seventh Washing. Eighth Washing. 



2 to 3 per cent, commercial vitriol. With very dilute caustic soda. 



This last product, termed white horse oil, is sold in competition with the American 

 petroleum. 



