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doi: 10.1111/j.1151-2916.1951.tb11644.xpmid: N/A
Magnesium carbonate, basic carbonate, and hydroxide were calcined at temperatures of 300° to 2000°C. for periods ranging from 120 hours at the low temperatures to a few minutes at the higher ones. The resulting magnesium oxides were studied by means of X‐ray powder diffraction and electron and petrographic microscopy. Only the cubic, periclase, crystal structure for MgO was observed. A small increase in the size of the unit cell was noted, however, for oxides obtained by low‐temperature calcination. Calcination of magnesium compounds was observed to take place in two distinct steps: (1) loss of gases at temperatures of 300° to 500°C. and (2) recrystallization or sintering at temperatures above 900°C. At the lower temperatures the loss of gases leaves a very porous structure with a large internal surface area and great reactivity (adsorptive power). Lattice dilation and imperfection is considered to account in part for the observed properties.
doi: 10.1111/j.1151-2916.1951.tb11645.xpmid: N/A
The effects of various oxide additions to specially prepared lime briquettes fired to 1625° and 1750°C. for 1‐ and 4‐hour periods are described as rates of hydration of the final product. The tests indicated that Fe2O3 was most effective in the reduction of the hydration rate. The method of incorporating the additive also controlled this rate. The studies included 1% increments up to a total of 5% of the following materials: Fe2O3, Cr2O3, V2O5, MnO2, CoO, TiO2, NiO, and Ca(PO3)2. Other oxides used without any noticeable effects were MgO, ZnO, Tho2, ZrO2, and SnO2.
doi: 10.1111/j.1151-2916.1951.tb11646.xpmid: N/A
The binary compounds Li2O.5Al2O3 and Li2O.Al2O3 can be formed easily by reaction of pure materials at 1500°C. The ternary compounds βeucryptite and βT‐spodumene and solid solutions involving these two compounds can be prepared by reaction of Li2CO3, Al2O3, and SiO2 at 1300°C. The thermal expansions of the lithium aluminates are very high, but the expansions of β‐spodumene and β‐spodumene solid solutions are very low. The compound β‐eucryptite is unusual in that it shows a high thermal contraction to 1000°C. Some relations between the expansion data and the crystal structure of the phases given above are discussed.
DIMMICK, H. M.; McCORMICK, J. M.
doi: 10.1111/j.1151-2916.1951.tb11647.xpmid: N/A
The limiting velocity of fracture for a soda‐lime glass was measured as a function of temperature over the range of 80° and 475°K. The value of the fracture velocity was obtained by electronically measuring the time necessary for the crack to travel between two platinum lines fired into the surface of the glass specimen. The value of the fracture velocity for this glass was found to be 1485 m. per second at 300°K. with the velocity decreasing slightly with increasing temperature over the range studied. The results indicate a temperature coefficient on the order of –0.15 m. per second per °K.
doi: 10.1111/j.1151-2916.1951.tb11648.xpmid: N/A
The effect of fluoride ions on the viscosity, yield point, pH, and conductivity of hydrogen‐clay slips and a calcium‐clay slip is shown. These data indicate that fluoride ions deflocculate hydrogen‐clay slips by the same mechanism as hydroxyl ions because these ions are isoelectric and approximately the same size. The data tend to confirm the electrocratic theory of deflocculation. The fluoride ion was not effective for deflocculating the calcium‐clay slip.
doi: 10.1111/j.1151-2916.1951.tb11649.xpmid: N/A
Thermal diffusivity data have been obtained on two typical soda‐lime‐silica glasses in the temperature range from 700° to 1400°C. The thermal diffusivity of a typical glass increases exponentially from 0.016 at 700° to 0.21 cm.2 per second at 1400°C. The measurement gives the total heat transferred by both conduction and radiation. The glass sample is held in a long crucible having cylindrical symmetry. A small sinusoidal temperature variation is superimposed on the mean temperature of the sample, and the time lag for the sinusoidal heat wave to travel radially from a point on the circumference of the sample to the center is measured. Furnace construction, method of controlling sinusoidal heat input, and methods of measurement are described.
doi: 10.1111/j.1151-2916.1951.tb11650.xpmid: N/A
The flame‐fusion technique is feasible for the growth of many anhydrous silicates. Successful syntheses were accomplished in four of the five classes of the general structural classification of silicates. There are several advantages for this type of growth technique, and an ideal opportunity is presented thereby for controlled experimentation in the study of natural and artificial crystalline structures, solid‐solution series, and the effects of minor additions.
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