774 SHALES AND MINERAL OILS 



Cast-iron stills are still preferred by some for the first distillation ; but the subse- 

 quent ones are usually performed in large malleable iron boilers of about 4,000 gallons 

 capacity. 



Befining Mineral Spirits. Much care is requisite in separating oils which issue 

 from the stills of such varied specific gravities. Were the light mineral spirit, or 

 ' aaphtha ' of the works, to enter largely into either the burning, or at all into the 

 lubricating oil, then would perish their reputation for safety. 



The naphtha is first sent over by steam from the boiler, containing oil in the second 

 stage of distillation. After being treated with 2 per cent, of sulphuric acid, and neu- 

 tralised with alkali, it is distilled again, by steam this time, at 13 Ibs. to the square 

 inch, and conducted by pipes down the sides of the still filled with naphtha, but 

 playing freely into it through punctures in the pipes covering the bottom. The liquid 

 is now ready for use in the paraffin-house, or for the special purposes to which it has 

 been applied in various arts. 



The Sc parating -house and Pressure-stills. At Acldiewell the contents of all the stills 

 are conducted into a separating-house, containing 15 separators, leading to as many 

 tanks outside. Here a man, by the aid of hydrometers, sends the oils into these varied 

 receptacles, according to their specific gravities. Until lately burning and lubricating 

 oils were the two marketable products, and the question rose, How to utilise the great 

 quantity of intermediates ? As a result of elaborate laboratory experiments, the appli- 

 cation of pressure to oils was found to diminish their gravity ; so pressure-stills have 

 been introduced. A pressure of 15 Ibs. on the square inch diminishes the specific 

 gravity 30. Thus intermediate oils can readily be converted into burning oil. 

 Large malleable iron stills, with pressure-gauges and loaded safety-valves, with like- 

 wise a valve at the neck of the still, are employed for this purpose. The pressure on 

 the oil-vapours themselves answers ; hence when the still is put in action the valve is 

 turned on at the neck, and the fires beneath well stoked till the pressure required is 

 indicated on the gauge, when the oil-vapours are allowed to flow into the condenser. 



Messrs. Henderson and Cooke have been able to dispense, at Oakbank, with the 

 tedious process of settling and its multitudinous tanks, by simply agitating the oil, 

 after it has come from the soda stirring-tank, with ground-glass or fuller's earth. This 

 process is patented. 



Preparation of Lubricating Oil and Paraffin. The blue oils with paraffin scales are 

 separated from the burning oil in the refinery after its treatment succeeding the second 

 distillation, and pumped up into a tank on the roof of the paraffin-refinery. It is then 

 sent through Henderson's cooling-drum, where the scale-paraffin crystallises out from 

 the slobbery liquid. It is now subjected in canvas bags to two hydraulic pressures, 

 whence commercial ' scales ' are obtained, and heavy oil containing soft paraffin ; this 

 again is separated by ingress into another cooling-drum, where it meets a brine-solu- 

 tion of 22 or 24 Fahr., from Kirk's ice-machine. The soft paraffin is thus thoroughly 

 taken out of its containing-liquid, which is now to be made into lubricating oil. It is 

 subjected to a 



First Washing. Second Washing. 



2 per cent, of vitriol. Strength as before. 1 per cent, caustic soda. 



DISTILLATION. 

 Third Washing. Fourth Washing. 



3 per cent, of vitriol. 1 per cent caustic soda. 

 It is then finished, though it is sometimes again distilled. 



PREPARATION OF REFINED PARAFFIN FROM SCALE. 

 First Washing. First Cooling in Drum. 



ird per cent, of its volume of hot naphtha. 



FIRST DRESSING. 



Second Washing. Second Cooling in- Drum. 



As before. 



SECOND PRESSING. 

 Third Washing. Third Cooling in Drum. 



THIRD PRESSING. 



Tenth. "Boiled with fane-black injacketted steam-bath. 



Twelfth. Filtered through Swedish blotting-paper in a stcam-jackctted filter, and run 

 into trays. 



Thirteenth. It may again be boiled in a jacketted steam-still, to as to expel att odour 

 of mineral spirits. 



