The humus content of raw samples of koalin, Kibushi-clay, Gaerome-clay, pyrophyllite, sericite, pottery stone and stoneware clay was determined by Tulin-Seki method.
Selected raw samples of Kibushi-clay and Gaerome-clay were treated with H
2O
2 and washed dist. water, then their dispersion, sedimentation volume, viscosity, plasticity, swelling and decomposition of Fe
2O
3 by introducing SO
2 in slip were compared with dist. water-washed raw clays.
Effects of humus upon loss, on ignition, thermal expansion and firing shrinkage were also studied.
The conclusions are as follows: (1) clays contain humus not a little, but no relati ons exist between its content and their color or name which suggests their existence; some Kibushi-clays have little humus; (2) no relations, are found between humus content and pH value or swelling of clays; (3) the decomposition degree of H
2O
2 to humus is independent by its concentration; (4) some humus is decomposed by H
2O
2 so readily, but another is not so; (5) H
2O
2-treatment of clay not only decomposes humus-clay-complex but also eliminates soluble salt, so that treated clay has much dispersion degree and increase in viscosity; (6) H
2O
2-treated clay has low sedimentation rate and high sedimentation volume; (7) humus in clay is decomposed at about 250°-550°C; (8) the decomposition of iron compounds in clay by introducing SO
2 gas in clay slip is accelerated by the addition of H
2O
2 in slip; (9) the amount of thermal expansion of humus bearing clay at the decomposion temperature of clay is less than that of H
2O
2-treated clay; but has much contraction at about 100°-200°C owing to absorbed moisture.
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