270 Mr. J. Napier on Copper Smelting. 



Should, for instance, the copper be in a certain stage of manu- 

 facture, and the coal contain much sulphur, the copper will be 

 deteriorated if too httle air be passing ; the sulphur will be merely 

 sublimed from the coal, and will combine readily with the copper. 

 Should there be sufficient aiv, the sulphui- will be burned or 

 converted into sulphurous acid, and the effects upon the copper 

 will not prove so deleterious. The same with the other ingre- 

 dients of the coal ; the carbon may either pass off as carbonic 

 oxide or carbonic acid, and the action of these in the fusing 

 chamber are different, and dependent upon the quantity of air 

 allowed to circulate through the fire. Every 6 lbs. of carbon 

 requires 8 lbs. of oxygen, equal to about 38 lbs. air, or 460 cubic 

 feet, to form carbonic oxide ; and it will require double these 

 quantities of oxygen or aii- to form carbonic acid. In the com- 

 bination of 6 lbs. carbon with oxygen, only a definite quantity of 

 heat is given out, which can be rendered less or more effective 

 according to the time taken to combine with the materials. Thus 

 if too little air be admitted into the fire, the combustion is slow, 

 and a ton of coal may be consumed without effecting the fusion 

 of the materials. The quantity of air, again, may be unneces- 

 sarily great ; and the heat so intense, as not only to fuse the 

 substances in the chamber, but also the materials of the fm-nace ; 

 so that the proper medium between these conditions is the object 

 of a good workman. 



Thus, it will be observed, a limit is put to the rapidity of the 

 operations ; were it not for this, the more rapid the fusion and 

 the stronger the coal, the better the smelted product. But the 

 material to be fused forms a solid mass upon the bed of the fur- 

 nace from six to twelve inches deep, and being a bad conductor 

 of heat it is transmitted through it slowly ; consequently a certain 

 time is required to fuse the whole, however intense the heat applied 

 may be ; but this intensity has to be limited by the tendency 

 which the bricks used for lining the furnace have for combi- 

 ning with the materials of the charge, and being thus destroyed. 

 It is easier and more (Economical to use a mixture of strong and 

 weak coal than to employ all strong and keep the combustion 

 low by regulating the draught ; and the superiority of a work- 

 man often consists in being able to use a greater quantity of 

 weak coal. The qualification of a workman is comprised in the 

 following : to do the greatest quantity of work with the least 

 quantity of fuel, having in it the greatest quantity of inferior 

 fuel, aud requiiing the least amount of repairs upon his furnace. 

 Indeed it would be worth the consideration of employers to 

 grant small premiums to the men who excelled in these qualifi- 

 cations. AVe have seen a furnace burnt down roof and sides in 

 twenty-four hours by a change of fuel and inattention on the 

 part of the workman. 



