Properties of chromite ores for the use of refractories manufacturing have been studied by many researchers. But chemical properties of the chromite ore fired in the air at relatively low temperatures have been little known. In this report, chemical behaviors of a Wakamatsu chromite ore, from Tottori in Japan, fired in the air at given temperatures below 1300°C were examined from the point of its reactivity in a definite reducing atmosphere of 99% CO-1% CO
2 or 40% CO-60% CO
2 gas mixture.
The following results were obtained.
(1) Catalytic decomposition of CO gas into carbon took place for the chromite ore which were fired at 700°C in the air, while for the ones which were fired over 700°C falled off the catalytic action.
(2) The samples fired in the air at temperatures below 900°C were easily subjected to reduction, while the ones which were fired over 1100°C were reduced only reluctantly.
(3) The iron component in the chromite ore was the most extractable with a hot solution of 6
N-HCl among the components in it, and the quantity of extraction was the largest in the sample which were fired at 700°C.
These results were interpreted as follows. In the chromite ore, the iron component is more unstable for heat treatment than any other and by its oxidation the sample may be brought to a unstable, chemically active state. Excessive heating over 700°C may cause it to fall into a stable state and make it less chemically active.
抄録全体を表示