reduction of the ores, fluxes, etc., will absorb for each lb. of iron yielded For the iron proper For the other elements 0. lb. 94 × 1887 = 1774 cals. 0. lb. 03 × 7000 = 210 " 66 therefore, the caloric absorbed by the reduction = 1984 66 And we may at once observe that of these 1984 cals. about 1700 are consumed in the upper part of the furnace, and about 250 to 300 in the lower regions of high temperature. To the caloric of reduction must be added that of the pigiron in fusion. This is composed of three parts-the caloric absorbed by pig-iron in its passage from ordinary temperatures to that of fusion-the caloric necessary for liquefaction (the latent heat of fusion), and lastly, that consumed by the pigiron in coming to the mean temperature of the hearth. Practically, however, these distinctions are useless. The essential is to know the total heat contained in the pig-iron as it runs from the furnace. This varies with the working of the furnace, and depends essentially on the mean temperature of the hearth, or, in other words, the degree of fusibility of the slags.* If the slags be refractory, such as earthy protosilicates, the iron will be hot, and will run from the tap at a higher temperature than if the slags be rich in manganese and in alkalies-or even if they be bisilicate of two or more bases. We need not therefore be surprised if the estimates of the total caloric of pig-iron, as given by different experimenters, do not agree with each other. Ordinary calorimeters were employed. The caloric taken up by the water from pig-iron in fusion poured into it was estimated. * See Note II. Appendix. M. Minary and Résal, experimenting with pig-iron fused a second time, just before it began to solidify, found 255 cals.* M. Rinman obtained from pig-iron of different brands, 261 cals., 257, 256, 252, and, on the whole, 46 calories would represent the latent heat of fusion.t Instead of 255, Messrs. Minary and Résal found the total caloric 292 calories, in experimenting with gray foundry iron. run from a cupola. But the cast-iron from the blast furnace is generally hotter than that of cupolas. M. Rinman found 300 as a mean for the cast-iron from charcoal furnaces with extremes of 270 and 311. Messrs. Boulanger and Dulait give‡— For forge iron-coke furnace For foundry iron. M. Vathaire, on the other hand, found§ For white iron For gray, No. 3 and lastly, Mr. Gillot, civil engineer, found for pig-iron run from a cupola, and as a mean of two experiments made at the blast furnaces of Bizy for gray iron from charcoal furnace. 309 cals. 337 66 280 cals. 330 66 337" Mr. Bell adopts M. Vathaire's figure, 330 calories: and this is the number we shall adopt for gray No. 3, until better informed. But it is evident that experiments have to be * Annales des mines, 5th series, t. xix. page 406. + Mémoire présenté à l'Académie de Stockholm, 15th May, 1865. § Etudes sur les hauts-fourneaux. multiplied, and especially the dependence of this number, 330, on the greater or less fusibility of the slags, and on the quality of the iron, has to be further examined. As a résumé, we may in the mean time adopt, as the caloric absorbed by the reduction of the ores, etc., and the fusion of the iron for gray forge iron, No. 3, § 12. Caloric absorbed by the fusion of the slag, the decomposition of the limestone, etc.-The slags have very different degrees of fusibility. Many years ago, Sefström and Berthier ascertained that bisilicates and even trisilicates of lime, magnesia, and alumina, are more fusible than the protosilicates, and generally the most fusible silicates correspond to compositions near to bisilicates.* It is on this account that the bisilicate formula is aimed at in all cases where the presence of sulphur or some analogous motive does not demand an excess of lime in the charges. And from this circumstance we see that not only the caloric absorbed by the slag, but that of the iron yielded, must vary, as above indicated, with the chemical constitution of the slags. The difference in the fusibility of slags has been proved by Plattner also, by comparing it with various alloys of gold and platinum. But if fusibility varies with the composition of the slags, so must the total caloric. The earthy singulosilicates, which are little fusible, must take more caloric than the bisilicates of these bases, or than the silicates containing a certain proportion of alkalies, and of * See Note II. Appendix. the oxides of iron and manganese. Hence, a diversity of results has been obtained by experiments on slags as by those on cast-iron. For a very irony slag from a cupola, MM. Mineray and Résal found 336 calories. For a slag, approximating to sesquisilicate of lime and of magnesia, M. Rinman found 441 calories, and for another 430. For a glassy slag from charcoal furnace, having manganese in its composition, and approximating to a bisilicate, M. Gillot found 370 to 380 calories. MM. Dulait and Boulanger found, for a slag of No. 3 iron, 433 calories, and for one from gray iron for foundry, 492. These two latter slags, like the most of slags coming from blast furnaces working with coke, are generally nearly singulosilicates. The first certainly contained oxide of iron. Lastly, M. Vathaire found, for a slag from a coke furnace yielding No. 3, 350 calories; and Mr. Bell found even 572 calories, but considers this number as a too high determination. From what precedes, we see that slags which are bisilicates and contain manganese, do not retain more than 370 to 400 calories in flowing from the furnaces, whilst sesquisilicates retain about 450; and that singulosilicates may take as much as 500 calories when they contain neither iron nor manganese, but, on the other hand, a high proportion of earthy bases. Again, Mr. Bell admits 550 cals. for the total caloric of slags of Cleveland No. 3 iron, by reason of their strong proportion of lime and alumina. In any case, the slags always retain more caloric than the iron. They have both a higher specific heat and a higher latent heat. This latter is as high as 120 cals., according to Rinman, for sesquisilicates, whilst that of cast-iron is only 46. But we see from the diversity of results, that in order to have an exact estimate of the caloric absorbed, we should have to make special experiments on each slag. We have more exact experiments on the caloric absorbed in the decomposition of limestone. MM. Favre and Silbermann found the number 373-5 calories for calespar, and 360-6 for arragonite.* Thus, in this case again, the molecular state has a certain influence on the caloricity, and it cannot be affirmed that every limestone, crystalline or amorphous, dense or porous, requires the same sum of caloric for its decomposition. Still, we may admit 373.5 for our present purposes. We have now to estimate the caloric absorbed by the vaporization and decomposition of water. For the evaporation we shall adopt Regnault's number, 606.5 calories. For the decomposition of water, we have 29,003 calories per lb. of hydrogen set free. This is the caloric produced by the combustion of hydrogen to steam. The result, therefore, is 29,003 3222 calories per lb. of water. 9 Let us remark in conclusion, that though the fusion of the slags absorbs caloric, the combination of silica and the bases probably disengages a certain amount of caloric which we cannot estimate. § 13. Sensible heat carried off by the Gases.-The caloric * Annales de physique et de chimie, 3d series, t. xxxvii. † 1 lb. hydrogen produces 34,462 calories, the steam being condensed to 00. If water remained in the state of vapor at 00, we must deduct 9 + 606·5 5458.5. Hence the figure 29,003 above given. Compare Bell, section xli. Tr. |