390 COKE 



ihe largest iron-works in the kingdom, and aro being erected at a number of other 

 works. The great saving in first cost of oven, economy in working and maintenance, 

 increased yield, and improved quality of coke, will probably soon cause this mode of 

 coking to supersede the others now in use. The kilns aro most advantageously mado 

 about 14 feet in width, and 90 feet in length, and 7 i'eet 6 inches in height ; this size 

 of kiln contains about 150 tons of coal.' 



From the long experience of this gentleman we are induced to quote yet further 

 from his memoir : 



' The process of coking converts the coal into a porous mass ; but this is done during 

 the melting of the coal, at which moment the gases in liberating themselves form very 

 minute bubbles ; but the practical result is the same as in wood-coal, allowing a large 

 surface of carbon in a small space to bo acted upon by the blast. As a general rule, 

 coke made rapidly has larger pores and is lighter than coke made slowly ; it accord- 

 ingly bears less blast, and crumbles too easily in the furnace. 



' The process of coking in the ordinary ovens may be thus explained : When the 

 oven is filled with a proper charge, the coal is fired at the surface by the radiated 

 heat from the roof ; enough air is admitted to consume the gases given off by the 

 coal, and thus a high temperature is maintained in the roof of the oven. The coal is 

 by this means melted ; and those portions of it which, under the influence of a high 

 temperature, can of themselves form gaseous compounds, are now given off, forming at 

 the moment of their liberation small bubbles or cells ; the coke now left is quite safe 

 from waste, unless a further supply of air is allowed to have access to it. At this 

 stage of the process, the coke assumes a pentagonal or five-sided shape and columnar 

 structure. When the coke is left exposed to heat for some time after it is formed, it 

 becomes harder and works better, from being less liable to crush in the furnace and 

 decrepitate on exposure to the blast. 



' It has been often remarked as a strange fact, that the hotter the oven, the better 

 the yield of coke ; hence all the arrangements of flues to keep up the temperature 

 of the ovens. This fact is, however, the result of laws well known to chemists. When 

 the coal is melted as above mentioned, the hydrogen in the coal takes up two atoms of 

 carbon for each two atoms of hydrogen, forming bicarburetted hydrogen gas (C 2 !! 2 ) ; 

 this at once escapes, but it has to pass upwards through the red-hot coke above, which 

 is at a higher temperature than the melted coal below. Now when bicarburetted 

 hydrogen gas is exposed to a bright red heat it is decomposed, forming carburetted 

 hydrogen gas (OH 2 ), and depositing one atom, or one half of its carbon, in a solid 

 form. Consequently in the process of coking, if the oven is in good working order, 

 tnd the coke hot enough, the liberated carbon is detained in its passage upwards, and 

 cither absorbed by the coke, or crystallised per se upon it. This is simply illustrated 

 by passing ordinary illuminating gas through a tube heated to a bright red heat ; 

 the tube will soon become coated internally, and ultimately filled with a carbonaceous 

 deposit produced by the decomposition of the bicarburetted hydrogen contained in the 

 gas. 



' It is found that some coal which is too dry or not sufficiently bituminous to coke 

 when put into the oven by itself in lumps, will coke perfectly if crushed small and 

 well wetted with water and charged in this state. This fact, if followed out, would 

 lead to an examination of the chemical nature of the effect produced by the water, and 

 would point the way to further improvements.' 



Charred Coal, as it is called, must be regarded as a species of coke. It has been 

 largely employed in lieu of charcoal in the manufacture of tin plates. This prepara- 

 tion was also a discovery of Mr. Ebenezer Eogers, who thus described its manufacture : 



The preparation of the ' charred coal ' is simple. The coal is first reduced very 

 small, and washed by any of the ordinary means ; it is then spread over the bottom 

 of a reverberatory furnace to a depth of about four inches ; the bottom of the furnace 

 is first raised to a red heat. When the small coal is thrown over the bottom, a great 

 volume of gases is given off, and much ebullition takes place ; this ends in the pro- 

 duction of a light spongy mass, which is turned over in the furnace and drawn in one 

 hour and a half. To completely clear off the sulphur, water is now freely sprinkled 

 over tho mass until all smell of the sulphuretted hydrogen produced ceases. Charred 

 coal has been hitherto produced on the floor of a coke oven, whilst red hot after 

 drawing the charge of coke. See TIN-PLATE MANTTFACTUBE. 



A process has for some time been gaining ground in France known as the ' Systeme 

 Appolt,' from its being introduced by two brothers of that name. Tho coking furnaces 

 employed are vertical, and they are in compartments. The authors published a 

 description of their process and a statement of its results, ' Carbonisation de la Houille 

 Systeme Appolt, decrit par les Auteurs, MM. Appolt Freres : ' Paris, 1858 ; to which 

 we must refer our readers. 



M. Copp6e has a coke oven which has been largely used in Belgium, and it has 



