In the couse of studying the influences of the heat action of igneous rocks upon the coal bed of Tagawa, the following measurements were carried out to find any good indicating properties which show the carbonization degrees of Japanese anthra cites. Estimation has been made of:
1. The density of coal in dry and ash free state
2. Ignition temperatures and electric resistances
3. The size of the unit crystallite in the diffraction of X-rays
As the results of these experiments, the following consequences became clear.
1. Beyond 90 percent carbon content in the course of the coalification process, the density of coal in dry ash free state shows a sudden increase with age and the electric resistance suddenly decreases. Therefore, both of them will become reliable indicators of the carbonization degree.
2. Ignition temperature gradually rises with age . So this will also become a good indicator of the carbonization degree.
3. The size of the unit crystallite becomes lager with age.
On the other hand, studying the influences of weathering upon the anthracites (Enokiyama), the following results were confirmed
4. Concerning Enokiyama weathered anthracites bed, judging from the quantitative analyses of humic acid and the results of infrared spectra of the samples taken from various depths, effect of weathering was found to be about 7 meters in depth from surface exposures.
5. As weathering advances, the amount of humic acid increases . Together with this change, the density of coal in dry ash free state shows a considerable increase and the electric resistance suddenly increases from 103 ohm to above 109 ohm. Therefore, both of them will become good indicators of the weathering degree.
6. Comparison of X-ray intensities of weathered anthracites with those of the unoxidized anthracites shows enhanced intensity of (002) band and nearly unchanged intensity of (10) band, and interlayer distance slightly shortens .
7. In the infrared absorption spectra, with the progress of weathering there appear and develop the absorption bands of 3.0μand5.8μ (du to-OH and C=O groups). The amount of oxygen in anthracites increases with weathering but H/C ratio is almost kept constant.
Judging from these facts, it seems oxygen is introduced only into the surface of crystallites of coal and hydrogen is not removed from them in the weathering process .