an was Na previous paper an attempt vore made carboy, the procese of smelting, it would of western Connecticut and of the extent to which iron mining has been carried on and is still being carried on in that region. It is perhaps even more interesting to trace the story of the ore after it passes from the miner's hands into those of the smelter and to see how prominent a place the iron-master has occupied in the history of the state. If iron ore were always a pure oxide, hydrate or carbonate of iron-if it were simply the metal combined with oxygen, oxygen and hydrogen, or oxygen and carbon-the be almost as simple practically as it is theoretically. The chemical and physical characters of the commercial ores were reviewed in the previous paper. Attention, however, again is called to the fact that these ores are practically four in number, namely, magnetite and hematite, compounds of iron and oxygen; limonite, a compound of iron, oxygen and hydrogen. and siderite or spathic iron ore, a compound of iron, oxygen and carbon. Theoretically the last two may be reduced to the condition of oxides by heat alone. In the case of limonite the hydrogen and a part of the oxygen are driven off in the form of vaporized water, and in siderite the carbon and a part of the oxygen are driven off as a carbonic acid gas, leaving the residue as a compound of iron and oxygen only. This, then, leaves all three ores practically alike and amenable to the same process for the final expulsion of the oxygen, when only the metallic iron will remain. The question now is, how to get rid of the oxygen. This is answered if we can find some substance which shall have a stronger attraction for oxygen than has the iron. This is found in carbon, and the fuel with which we heat the iron furnishes this element. Theoretically we have only to heat the iron with a plentiful amount of fuel assisted by a proper supply of air. The oxygen of this air is necessary to burn the coal, the result being carbonic acid gas. But not all of the carbon of the coal is thus consumed. Under the influence of the heat, the remaining carbon having only a partial supply of oxygen, wrests the oxygen from the ore, combines with it and passes away as carbonic acid gas also, leaving behind the pure iron which is desired. This is the theoretical process of ironsmelting. The practical process which is based upon it would be equally simple, but for two obstacles. The first is the difficulty of supplying such perfectly balanced amounts of carbon and oxygen as shall do the work without leaving a residue of either. The second is the presence of certain impurities in both ore and fuel which form new and undesirable compounds and materially affect both the economy of the process and the value of the iron produced. To modify the theoretical process so as to overcome these FURNACE NO. 3. THE HEARTH. (The opening at the right is for running off the slag, that at the left for drawing off the iron. The pipes carry water for cooling the walls of the hearth.) be eliminated entirely, when desired, by a subsequent process. The second obstacle is a far more serious one. The presence of sulphur or phosphorus is extremely detrimental to the quality of the iron, the former rendering it liable to crack when worked at a high temperature, the latter, when it is worked cold. Sulphur can be driven off to a considerable extent by a preliminary roasting of the ore, but the 234 last traces of both are very hard to eliminate. There are other impurities, mostly of a silicious nature, which are found always to a varying extent in the ore. These are eliminated by smelting, but in the process they combine with a portion of the iron itself, producing a troublesome slag within the furnace and materially reducing the amount of pure metal finally obtained. In practical smelting this obstacle is overcome by adding a certain amount of "flux," usually limestone, to The lime takes the place the ore smelted. The lime takes the place FURNACE NO. 3. TWYER ARCH. of the iron in the slag and the lime-slag The device universally used at the 66 is the which floats on the surface of the liquid escape Of The chemical reactions which go on inside the furnace are not quite so simple as the previous statement would suggest -the statement represents, practically, The heated gases of the final result. various kinds which issue from the top of the stack may be allowed to directly into the air where they burn, or, more frequently, they are utilized. course the introduction of cold air into the furnace through the twyers tends to reduce the temperature of the interior and causes a distinct waste of heat. all blast furnaces of the present day it is the practice to heat the blast to a very high temperature before it enters the twyers, and for this purpose the exceedingly hot gases which escape at the top In of the furnace are utilized. The blast is, however, sometimes heated by separate fires. These are the essential features of the blast furnace. Its product is known as "cast iron." This is iron with which is combined a considerable amount of carbon. Cast iron is fusible and, upon being suddenly "chilled" when hot, becomes very hard and brittle. But this "chilled" iron is not capable of taking a temper nor does it possess the extreme ductility and malleability necessary for certain commercial uses. These are only obtained by subjecting it to a process of "refining," which removes the carbon and leaves what is known as "wrought iron." This cannot be melted, but can be heated to a plastic condition when it can be wrought into any shape desired. It always retains its wonderful tenacity, but can be neither tempered nor chilled. Intermediate between cast iron and wrought iron, both as to the amount of carbon contained and the qualities possessed, stand the "steels." Steel may be melted and chilled like cast iron, but, by a subsequent re-heating and by a gradual cooling carried to exactly the right point, it may be "tempered," that is, brought to a condition where hardness and elasticity are balanced to any desired degree. The manufacture of steel may be considered, in the present case, as a matter by itself, but the process of refining cast iron should receive some mention, as it held a prominent part in the iron industries of Connecticut. The refining of cast iron is carried on in several different kinds of furnaces, though what is known as the "puddling" furnace is perhaps the most important. In all cases, however, the process is essentially the same and consists in re-melting the pig iron and subjecting it to a draft of air. As a final (O, oven. A, B, C, pipes for heating blast. D, E, G, pipes carrying blast to twyers, TT.) collected into masses called "blooms which are extracted from the furnace and are subjected to blows of a power hammer. This squeezes out all slag contained and compresses the spongy mass into a solid piece which is subsequently re-heated and rolled. Under primitive conditions of iron smelting, where ore was rich and charcoal plenty, wrought iron was often produced directly from the ore, but at a great sacrifice of iron and fuel. The process was essentially the same as that of refining, except that the ore itself was treated instead of cast iron. The furnace in which this was done was known as a "forge." These are still in use in the Adirondack region. It is rather a common idea that all that is necessary to render a locality an iron producing region is the presence of rich DIAGRAM OF BLOWING ENGINE. (A and B, blowing cylinders. C, water wheel.) ore in sufficient quantity. Strangely enough, however, in this era of economic production this is almost the last requisite. A very large part of the English iron producing ores are of an inferior quality, much below many ores which are allowed to lie unused in this country. What is really necessary is that the three essentials -ore, fuel and flux-shall exist in close proximity. When, in addition, the ore. is rich and pure, the conditions are ex ceptionally good for the establishment of a great industry. For many uses the best grades of iron are not at all necessary and the cheaper product will fill all needs. It is for these reasons that the furnaces of Connecticut, which produced the best iron that this country has ever known, are cold to-day. Exceptional ore and abundant flux are there, but fuel is wanting. In consequence the output must be small and the price per ton high. Of late years steel has become so cheap that it is used for many purposes for which iron was formerly employed; and it is a curious fact that the brown hematite of Connecticut, while producing the best of cast and wrought iron, is not a good steel ore. Nevertheless, the demand for this iron for certain special uses, notably for the manufacture of car wheels, will always keep the industry alive. But if we return to a time when the life of the country was massed along the eastern seaboard, when the great iron and coal fields of the continent had not been even explored, we shall see that Connecticut possessed all the requisites and enjoyed all the prestige of a great iron region. The history of the development of the industry, will however, have to be postponed to the third and last paper of this series, although it is almost impossible to exclude all history from a consideration of the industrial and economic phases of the subject. The fuel for the modern blast furnace is mineral coal, although this has to be coked before it comes in active contact with the ore in order to drive off the impurities which would be detrimental to the finished product. In the earlier forges and furnaces charcoal, which is free from these impurities, was the universal fuel and Connecticut possessed abundant facilities for producing this. Scattered through the chief iron bearing region of the state |