Bulletin . Figure 2.—Section through platinum-wire resistance furnace, a, Heraeus tube fur-nace, type B; 6, porcelain tube, 2| inches in inside diameter and 12 inches long,wound with a platinum-foil heating element; c, alundum tube, li inches in insidediameter and 6 inches long, with &-incb wall; d, 17 feet of platinum wire 3/100 ofan inch in diameter, wound on the inside of tube c, six turns to the inch in themiddle and closer at the ends to compensate partly for the radiation at the ends ; e, alundum extraction thimble No. 5811, 30 mm. in diameter and 80 mm. long; f, g, and h, i, alundum dis
Bulletin . Figure 2.—Section through platinum-wire resistance furnace, a, Heraeus tube fur-nace, type B; 6, porcelain tube, 2| inches in inside diameter and 12 inches long,wound with a platinum-foil heating element; c, alundum tube, li inches in insidediameter and 6 inches long, with &-incb wall; d, 17 feet of platinum wire 3/100 ofan inch in diameter, wound on the inside of tube c, six turns to the inch in themiddle and closer at the ends to compensate partly for the radiation at the ends ; e, alundum extraction thimble No. 5811, 30 mm. in diameter and 80 mm. long; f, g, and h, i, alundum disks; ;, observation hole ; k, thermo element made of platinumand platinum-rhodium ; I, ash Figure 3.—Meker muffle furnace No. 29. a, Magnesite muffle; b. Meker blast burner;c, ash cone ; d, removable fire-clay door with horizontal slot for thermocouple tube e. in different types of furnaces such as are in more or less common usefor such tests. Each of these furnaces has its own particular atmos-phere—oxidizing, reducing, or neutral—which is the principal cause EXPERIMENTS WITII SEGER CONES. 23 of the large variations that were found on comparing the softeningtemperatures of the same sample in the different the comparative tests six furnaces were used, as follows:1. Platinum-wire resistance furnace (fig. 2). having an oxidizingatmosphere of air, with absolutely no reducing gases present.
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectminesandmineralresou
