SHALES AND MINERAL OILS 771 



and while it is being burned under the boiler, the elastic force of heated vapour is 

 made to produce a blast of air so as to ensure perfect combustion. This was first 

 applied in a coal-tar distillery. The time for running & charge of tar through the 

 stills was thus reduced from 24 to 12 hours. And the stills so fired do not require so 

 frequent repairs as those worked with coal. Indeed, such applications of heavy 

 oil appear to be very economical. In Mr. Miller's Works, Rumford Street, Glasgow, 

 a con of dead oil, valued at Id. or 2d. per gallon, appears to do the work of 1 ton of 

 coal at least. 



In certain metallurgic operations at Woolwich, about 8 cwts. of liquid fuel were 

 found equal in value to a ton of coal. One-fourth or one-fifth of the time occupied 

 in heating with. coal was saved, and a smaller number of furnaces were required. In 

 heating a half-inch plate, 4 or 5 minutes served with liquid fuel in opposition to 

 15 or 20 minutes with coal. While a four-inch armour-plate took 3 hours in 

 heating with coal, a very much better article was completed in 38 minutes with liquid 

 fuel. 



The different Mineral Oils. The nomenclature of mineral oils is very obscure. It 

 has partly originated from scientific discoverers ; partly from tar-distillers who have 

 been struck by the similarity of the educts from retorts or stills to those with which 

 they have been familiar; and partly from the trade-marks of merchants. Eupion, 

 photogon, kerosene, Cambrian oil, shale oil, Boghead naphtha, shale-naphtha or oil, 

 paraffin oil, coal 'oil, are all synonymous for the article used in the German lamp. 

 Then, again, all oils too high in sp. gr. to be used in such lamps were ranked as 

 lubricating. But recent improvements in lamps for burning these heavy oils have 

 caused the intermediate oils, betwixt 830 and 880, to be sub-classed as lamp oils, 

 lighthouse oils, railway-carriage oils, according to their several specific gravities. 

 Blue oils or green oils are the refiner's terms for certain of his intermediate products 

 which used to bo in demand by grease-makers or printing-ink manufacturers. He 

 describes other bye-products, as soda-tar and acid-tar ; but we are in ignorance as to 

 the true chemical nature of these bodies. Hard and soft paraffin correctly enough 

 describe the solids sold respectively to the candle- or the lucifer-match-maker. 

 ' Foots,' ' bottoms,' or such like names, have been borrowed from the tar-distiller to 

 signify the refuse products of the stills. ' Scales ' expressively denotes the paraffin 

 pressed from the blue oil, to be subsequently refined. ' Naphtha ' incorrectly desig- 

 nates the first product of the distillation of coal- or shale-tar, as the aniline-maker 

 cannot find in the latter benzol, the foundation of his specialty. ' Coke,' however, 

 truly describes a valuable bye-product obtainable at several stages of mineral-oil 

 refining. 



The prefix ' paraffin,' either to the lamp-oil or to mineral machinery-oil, is a mis- 

 nomer, as there is none of that substance in either of these bodies. The proximate 

 constituents of petroleum are the paraffin series ; b.ut mineral oils only contain th 

 or |th of these, their chief constituents being the oletiant-gas series. 



Shale-tar, a local designation for crude oil, is correct enough when limited to the 

 products of destructive distillation by a low red-heat, of sp. gr. 840 upwards. But a 

 tar sinking in water might be obtained by the application of a bright cherry-red heat 

 in distilling shale ; and the converse is true of coal. The following scheme expresses 

 to the eye the order of production of the various products : 



Yield from distillation of Crude Oil obtained from Coal or Shale, or from Petroleum 

 got from natural Springs. 



(RECTIFIED SPIRITS or BEXZINE. 

 1. BURNINO OIL. 

 2. ACID TAR EESIDUES. 

 3. SODA TAR RESIDUES. 



HEAVY OILS rectified, be- "I , .-, ,-. , , ,-, ,, 



lrl - 9 , /, 1 1- CRUDE PARAFFIN. /I. REFINED PARAFFIN. 



residues . S J 2 " BLUB "- i 2 ' MACHINERY OIL. 



Residues may be used for greases, gas-making, patent fuels, &c. Gases may bfl 

 used for heating. 



Except in the case of the crude oil, which is of a dark greenish, viscous nature, 

 analogous to tar, of the intermediate blue and green oils, which are sufficiently desig- 

 nated by their appellations, all the liquid products are now made as near water-white 

 as possible. A burning oil is reckoned perfect in colour not only when it attains such 

 purity, but when it also has the bluish opalescence so characteristic of refined 

 petroleum. No doubt refiners here pander to a popular prejudice; for in striving 

 after this standard of colour they diminish the burning qualities of their oils. 



