U2 



THE REFUSE OF THE SMELTING MACHINE. 



[1855. 



Lime, from Marmora, McNab, Lcs Chats, Gloucester, Montreal, Pack- 



enham and Cauglinawaga. 

 Trap, from St. lloch. 

 Marble, from Oxford, Brompton Lake, Dudswell, St. Armand, St. Lin, 



McNab and Pakenham. 

 Hydraulic Lime, from Thorold, Quebec, Oneida, Nepean and Brant- 



forJ. 

 Bricks for Building, from various places. 

 Peat, from Longueuil and Sheifield. 

 Asphaltum, from Enniskillen. 

 Aerolite, found in Madoc, forming a mass of Iron with 6.35 per cent. 



of Nickel, -weighing 370 lbs. 



TIic Refuse of tlie Smelting FiUJiacesi- 



The production of iron by the smelting-furnaces of Great Britain 

 has reached 3,000,000 tons annually; and by a moderate calculation, 

 it may be assumed that for every ton of iron two tons of slag are 

 formed, making an aggregate of at least 6,000,000 tons of this hitherto 

 refuse material. Not only has this vast accumulation of slag been to 

 the present time comparatively useless, but it has proved an incum- 

 brance and source of heavy expense to the ironmasters ; for it is 

 calculated that a sum of not less than £1.50,000 sterling is annually 

 expended by and lost to them in removing the unsightly heaps from 

 their premises, to be used as the most worthless of materials in 

 mending old roads, and in filling gullies and other vacant spaces. 

 We are, however, destined, before long, to witness this singular sub- 

 stance applied to economic purposes of the highest utility; and we 

 venture to predict that it will be hereafter seen superseding the labours 

 of the quai-ry, rivalling the most valuable marble, and even in beauty 

 and brilliancy many of the precious stones, such as the agate, the jasper, 

 the different classes of variegated marbles, and even the very attrac- 

 tive malachite. 



We now proceed to notice a highly interesting paper, read at the 

 Society of Arts, by Dr. William H. Smith, of Philadelphia, U.S., "On 

 the Utilisation of the Slags, or Molten Mineral Products of Smelting 

 Furnaces." The term " slag" has been defined by most standard 

 authorities as the "refuse vitreous products of smelting furnaces," a 

 definition which, being only applicable to slag in its altered conditions, 

 after having been rendered brittle and worthless by improper treatment 

 succeeding its withdrawal from the smelting furnace, he rejects as 

 erroneous. In order to be fairly viewed and justly appreciated, slag 

 must be considered both in its molten state, as a fused miner.al pro- 

 duct, and in the variety of combinations, forms, and general proper- 

 ties it may be made to assume, under scientific treatment, subsequent 

 to its removal from the smelting furnace. The first general view 

 which slags thus considered naturally present, is that which relates to 

 their philosophic character, which we briefly notice before passing to 

 consider a more important aspect — viz., their commercial value. 



In the wide range of geological science we find but few general 

 phenomena which cannot be elucidated by the chemico-mineralogical 

 transformations of the smelting furnace. In that vast apparatus, by 

 the study of existing operations, agencies, and laws, the geologist 

 finds a clue to the formation of the earth, an exponent of those laws 

 and phenomena which have modified and determined the condition of 

 the rocky crust of the globe. When his cupola is built, and his blast 

 started, the metallurgist is at once ready to daguereotype, or rather 

 reproduce, although in minature, the mountainous deposits and diver- 

 sified formation of the igneous rocks; and if his researches verge 

 upon chemical science, in studying the agency of heat on the form 

 colour, and other properties of matter, he can observe the influences 

 which determine the crystaline or amorphous structure of slag, and 

 those wonderful chemical afiinities which bind together in definite 

 atomic proportions the elementary molecules of slag, however complex 

 the combinations it may assume under the smelting operation. 



The rocks of igneous origin are well known to the scientific world, and 

 highly appreciated by the practical architect ; they ai'e the rocks of 

 which Nature builds her loftiest mountains, and man constructs his 

 most enduring monuments. Many of the mountain ranges even of 

 this island are composed of those strata which have been thrown up 

 and altered in mineral aspect by molten masses and veins, presenting 

 no ti-aces of decomposition, and which, like slag, are of igneous origin. 

 Granite, syenite, protogine, serpentine, poryhyry, basalt, felspar, 

 greenstone, lava, &c., are amongst the varieties of the igneous rocks, 



* The Mininff Journal. 



and the industrial purposes to which they are applied are numerous, 

 and of primary importance. If we admit the existence of some deep- 

 seated source of heat to which these rocks owe their origin, the anagoly 

 between them and the products of smelting furnaces, which are 

 composed of the same elements, fused by the same igneous agency, 

 and modified in form, colour, and character, by the same fixed chemical 

 laws, a doubt cannot be entertained of the value of this artificial 

 mineral product, as combining in itself qualities possessed and divided 

 amongst many natural varieties. Selecting the slags of iron furnaces, 

 they will be found composed of silica, lime, and alumina, as their 

 chief ingredients, in combination with traces of magnesia, protoxide 

 of iron, sodium, potassium, carbon, manganese, carbon, sulphur, 

 titanium, and phosphorus. According to the analysis of M. Berthier, 

 the slag of the Dowlais furnaces, from which some of the manufactured 

 samples exhibited were made, consists of silica, 40'4; lime, 38'4 ; 

 alumina, 11-2; magnesia, 5-2; protoxide of iron, 3-8 ; and a trace of 

 sulphur. Slags from Dther iron furnaces in France and England pre- 

 sented similar analytical results, varying slightly as to the relative 

 quantities of manganese and sulphur, while a mean average of the 

 anthracite fm'uaces of America shows their slag to consist of silex 51, 

 lime 21, and alumina 15. Prof. Philips, in his mineralogical work, 

 observes: — " If we look more nai'rowly into the composition of the 

 crust of the globe, as consisting chiefly of the earths and earthy ma- 

 terials, we find that only three of the earths which have been 

 discovered — viz., silica, alumina, and lime, are found to constitute its 

 great bulk." Regarding, therefore, silica, lime, and alumina, as the 

 chief constituents of slag, we are furnished with the very ingredients 

 out of which Nature has fashioned and annealed nearly all the valu- 

 able building materials of the mineral kingdom. 



In the utilisation of slag for commercial purposes, by the processes 

 of casting, pressing, rolling, moulding, and annealing, the facilities 

 afforded by the extremely liquid molten state to which the slag is re- 

 duced in the smelting furnace are availed of, so that by suitable 

 appliances any desired form, colour, or texture, can be imparted. We 

 here adopt the descriptive language of Dr. Smith: — "According to 

 tlic treatment it receives, slag can be rendered brittle Or tough, hard 

 or soft, compact or porous, rough or smooth. It can be cast into as 

 great a variety of forms, solid and hollow, as iron itself, with the 

 superior advantage of being susceptible of the admixture and blend- 

 ing of colours, so as to render it equal in brilliancy to agate, jasper, 

 malachite, the variegated marbles, and other more valuable varieties 

 of the mineral kingdom. AVhen properly annealed, it can be made to 

 acquire a surface, or texture, at least 10 times as durable as that of 

 m.arble, and is susceptible of a polish equal to agate or cornelian. As 

 a building material slag can be readily adapted to any variety of archi- 

 tectural design, from the simple slab to the most ornate and complex 

 decoration ; whilst its beauty and durability chiefly recommend it as 

 an article of luxury." 



Dr. Smith entered into a comparison of the relative expense of the 

 manufacture of clay bricks as compared with that of bricks oi' blocks 

 of slag ; and he reminded us, that in making bricks of the latter, the 

 raw material cost less than nothing, inasmuch as the ironmaster saves 

 by its utilisation the heavy expenditure now attendant upon its re- 

 moval from the furnace premises. In fusing slag for the operation of 

 casting no expense is incurred, inasmuch as this item of expenditure is 

 charged by the metallurgist to the metallic and not to the earthy pro- 

 ducts of the smelting operation ; whereas, in making bricks of clay, 

 the raw material has an intrinsic value, while the consecutive oper- 

 ations of digging the clay, preparing it for use, and transporting it, 

 added to the process of pressing and .annealing, consume at least twice 

 as much time and laboui- as are employed in working slag. "From 

 these simple, yet clear data," observed Dr. Smith, " we can fairly in- 

 fer that the cost of making clay brick will be double that of making 

 blocks, tiles, or more decorative and valuable articles from slag. By 

 extending this calculation to other products, such as marble slabs, 

 columns, carved architectural ornaments of stone, &c., and in our 

 estimate contrasting the plastic power of fusion available in slag with 

 the laborious hewing and fashioning by mechanical means required 

 for blocks of marble and other stones, we may arrive at still more 

 satisfactory results in proving the commercial value of slag." 



The samples which were exhibited and examined by the auditory 

 excited general admiration, from the closeness of the texture, the 

 height of the polish and the beauty .and apparent durability of the 

 articles. Some of them had been made from the slags of American 

 furnaces, others from those of the furnaces of France and England ; 

 and it was evident, from their inspection, that tlie commercial value 

 expressed in the above calculation was by no means extravagant. To 



