In order to solve the cause of “bursting” of chromite series refractories, spinel, picrochromite, magnesioferrite, forsterite, clinoenstatite, monticellite, Fe
2O
3⋅2Cr
2O
3, and Fe
2O
3⋅2Al
2O
3 were prepared by chemicals and some of their properties were determined. Data for the interplanar spacing, microscopic observation, firing shrinkage, colour in bulk and magnetic property were given.
The most important result is as follows: In the case of the mixture blended MgCO
3:Al
2O
3=1:1, the products fired at 1500°C. and 1780°C. showed the same X-ray diffraction patterns, both corresponding to that of common spinel. Their lattice constants obtained by Debye-Scherrer's method were quite identical, 8.06
6 kX, though there were slight differences between their synthetic rates (94.94% in the product fired at 1500°C. and 95.31% in that fired at 1780°C), their grain diameters (33.9 and 55.2 micron), their refractive indices (1.716 and 1.718), and true specific gravities (3.61
6 and 3.62
5).
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