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doi: 10.1111/j.1151-2916.1921.tb17355.xpmid: N/A
ABSTRACT In this paper the relation between the composition of barium glasses and the optical constants is discussed as well as the general rules for proportioning batches. The important results and conclusions are given by the figures. After the required amounts of BaO and B2O3 have been obtained from figures 2 and 3, the amount of SiO2 can be obtained from figure 5, the alkali and ZnO from figure 7 and the Al2O3 from figure 8. If the total exceeds 100, the ZnO and the Al2O3 may be reduced. The proportions cannot be as definitely expressed as in the case of lead glasses and more experience is required to enable one to change the optical properties at will.
doi: 10.1111/j.1151-2916.1921.tb17356.xpmid: N/A
ABSTRACT Metallography of Low Carbon Steel.—A discussion of the cooling of steel through the critical range is followed by a consideration of the general structure of low carbon material. A brief discussion of mechanical and thermal treatments follows including the statement of the essential conditions for annealing. Investigation of Oxy‐Acetylene Welds.—The temperature reached by the steel in the enameling operation is discussed with reference to the annealing temperature. An examination of plates and welds before and after enameling shows that a thorough annealing of the weld has been accomplished.
doi: 10.1111/j.1151-2916.1921.tb17357.xpmid: N/A
ABSTRACT Calcination.—Magne ium carbonate in dolomite is decomposed by calcining for one hour at 800°C. Calcium carbonate is not completely decomposed until after calcination at 960°‐1040°C for one hour. Treatment with sulphuric acid.—By adding sufficient H2SO4 to milk of dolomite to react with the lime present, a bulky precipitate of Mg(OH)2 is formed which may be partially separated from the finer CaSO4 by screening through a 120 mesh sieve. The residue on the screen contains about 68.3 per cent MgO and represents over 50 per cent of the original CaMgO. Flotation.—The best results by flotation were obtained by removing the fine material from the raw dolomite and then calcining at 920°C. Wood creosote flotation oil number 400 was found best suited for this separation. The concentrates removed by flotation, however, represent only 25 per cent of the dolomite originally treated. Leaching and screening.—By a leaching and screening treatment it is possible to obtain a product containing about 80 per cent MgO. This is superior to Canadian magnesite in MgO content. Elutriation.—By an elutriation treatment it is possible to obtain a residue containing over 85 per cent MgO and representing about 30 per cent of the, original dolomite.
doi: 10.1111/j.1151-2916.1921.tb17358.xpmid: N/A
ABSTRACT Preparation of the Cement.—Crystalline magnesite from Washington was crushed to three sizes—to pass a No. 6 sieve but retained on a No. 10; between a No. 10 and a No. 30 and to pass a No. 60 sieve. These sizes were burned separately in an electric rotary kiln at 600°, 650°, 700°, 800°, and 900°C. Tests of the Cement.—The cement was tested in three flooring mixes in which the MgO was 35.0, 42.5 or 50.0% by weight, and in three stucco mixes in which the MgO was 11, 22 or 33% by weight. Tensile and compressive strength specimens were broken at 24 hours, 7 and 28 days. The coefficient of expansion was determined at 48 hours, 4, 7, 28 and 90 days. Other properties determined were time of set, consistency, soundness, fineness and effect of density of the chloride solution used. Results.—The property of the calcined cement is materially affected by the size of ore, temperature and duration of burning. The rate of reaction of MgO with chloride materially decreases with increased temperature of burning. Decreasing the concentration of the magnesium chloride solution (down to 22° Bé) accelerates the set of freshly calcined magnesite and retards the set of magnesia which has become hydrated to a considerable extent through exposure. Exposure to moisture before using as well as increasing the consistency of the mixture lengthens the setting lime. A composition which expands excessively and warps or buckles is not necessarily “unsound,” but one which disintegrates within a comparatively short time may be considered as such. Used in this sense, “unsoundness” is believed to result from the presence of free magnesia which hydrates after the mixture has hardened, and not from the presence of lime. Therefore, soundness is not a property of the magnesia alone but depends upon the extent to which it reacts with the magnesium chloride, water, or carbon dioxide before hardening takes place and upon the amount of hydration which subsequently occurs. The steam or cold water tests are unsatisfactory as accelerated tests for soundness of magnesia mixtures. Under the conditions of these tests, the best material with regard to setting time and strength was produced at a temperature of 800°C. However, the magnesia burned at 650°C and which gave comparatively very low strength when gaged with a 22° Bé solution of magnesium chloride, gave excellent strengths when gagrd with more concentrated solutions. Materials tested with 22° Bé solution and giving satisfactory results would not necessarily be satisfactory with a higher or lower concentration. It seems that general specifications should also include limits corresponding with tests in which higher and lower concentrations are used. No relation was found between the volume change and any other property of the magnesia. Tests of any particular mixture are no indication of the behavior of the same magnesia in other mixtures. However, the laboratory tests indicate that the leaner mixtures undergo less change in volume than the richer ones. Furthermore, a number of strict comparisons between laboratory and field tests indicate that the laboratory tests of volume changes as made are no index to the behavior of the material under actual service. The lean mortar mixture proved to be the most suitable of any used for testing magnesia, and in this case the tensile strength furnished as much, if not more, information than the compressive strength.
doi: 10.1111/j.1151-2916.1921.tb17359.xpmid: N/A
ABSTRACT Design of a natural‐gas furnace for annealing optical glass.—Most of the furnaces built for annealing regular glassware are unsuitable for optical glass due to irregularity and inequality of temperatures. Working drawings are given for a successful optical glass annealing furnace operated by natural gas. The design is novel in the placing of the flues and burners in such a manner as to supply the heat and remove it in a symmetrical manner, thus obtaining uniformity of temperature.
doi: 10.1111/j.1151-2916.1921.tb17360.xpmid: N/A
ABSTRACT Commercial fire‐clay tiles, were tested at furnace temperatures, for transverse strength. This was supplemented by tests of tiles of known composition made in the laboratory. Moduli of rupture obtained varied from 245.5 pounds per square inch at 1275°C, to 28.9 pounds per square inch at 1350°C but the data collected do not warrant definite conclusions.
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