The calorific value of coal in the Yeban coal field changes from 6, 400 (d. a. f.) kcal/kg to 8, 190 (d. a. f.) kcal/kg. The general results on microlithotype of coal by petrographic analyses changes from 19.6‰ to 63.3‰ in vitrite, from 17.1 ‰ to 63.2‰ in durite, from 14.1‰ to 21.1‰ in clarite and from 0.1‰ to 3.6‰ in fusite (Fig. 6).
Durite is richest, clarite is the second and vitrite is the third, in carbon (d. a. f.), hydrogene (d. a. f.), volatile matter (d. a. f.) and calorific value (d. a. f.) (Fig. 4, 5).
The coal in the Northern Iwaki district is the richest in durite, calorific value (d. a. f.) and volatile matter (d. a. f.), and is the highest in rankham other districts. These values are decreasing in order of the Futaba, Taga and Southern Iwaki districts (Fig. 6).
As the depth of coal seams in each district increase, the calorific value (d. a. f.), degree of coalification and content of durite increase, while the content of vitrite decreases (Fig. 1-3. 7). The causes of regional difference in the degree of coalification are as follows:
(1) The coal in the Northern Iwaki district was affected by geothermal metamorphism (Fig. 8).
(2) In the Taga district, coal was affected by the dynamic metamorphism (Fig. 1).
(3) The geological age (Early Miocene) of coal in the Southern Iwaki district where the rank is lowest, is younger than that (Oligocene) in the other districts.
While, it is presumed that the aquatic dendroid plants grew on shore in the plant accumulating basin, the aquatic herbs grew off-shore in the basin; and there was two types in the plant accumulating mechanism the subsidence and upheaval. In the case of subsidence, as the basement of basin subside, the coastal plain turns into the swamp where the vegetation grow, and, then the thickness and width of the layer of plant accumulate. In the case of upheaval, as the basement upheave, the marginal area of basin turns into the land, and then the thickness and width of layer decrease. Joban coal field belongs to the type of subsidence (Table 1, Fig. 9, 10).

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The present report concerns with the contents of the oxygen containing groups in the artificial coalification products (C‰, 60-80) of the low rank coals in Hokkaido (Tokachi lignite, Tsuchiya lignite and Tenpoku coal) and the results of estimation were compared with those of natural coals in order to make clear the artificial coalification mechanism.
Acetylation method modified by Takeya and co-workers was used for the measurement of hydroxyl group.The carbonyl-carboxyl-and methoxyl groups were measured by oxidation method, ion exchange method with barium acetate and Zeisel's method respectively.
The distribution of the oxygen containing groups in the artificial coalification products of the low rank coals was generally similar to that of natural coals. The contents of the oxygen containing groups (-OH-CO, -COOH, -OCH₃ and C-O-C) in coalfication the artificial coalification products decrease with increase of their carbon content. The distribution of the oxygen containing groups of the artificial products of Tokachi lignite bus the same tendency with that of natural coals. It may be concluded that the contents of the oxygen containing groups in the artificial coalification products decrease with the increase of the time and temperature of artificial coalfication from the view points of the artificial coalification temperature-the atomic ratio, O' (oxygen containing group) /C' diagram, the artificial coalification time-the atomic ratio, and O' (oxygen containing group) /C'diagram.

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In order to elucidate the chemical structure of the parts which are destroyed in the transition from low rank coal to humic acid, chemical and infra-red spectroscopic examination of the solid products obtained byHNO₃-oxidationn and wet O₂-oxidation of coals were tried and also their reactioncharacteristics were compared with those of various model compounds.
Three kinds of coals (C=76.2‰I, 70.9‰II, 67.9‰III) were oxidized with 12. 7 HNO₃ at 80°C. The lower the rank of coal was, the more it is reactive toHNO₃. Infra-red spectra of their solid products suggested that in the process of coal oxidation formation and destruction of phenolic OH group took place consecutively.Molecular weight of humic acid decreased with lowering of the rank of parent coal. The comparison of the composition of humic acids with their parent coals showed that in II and III, the part near H/C=1 in coal molecule was destroyed inthe process of humic acid forma-tion, however, in I hydrogen rich part was attacked NO rich gas was evolved in oxidation of low rank coals with diluteHNO₃ and the composition of gaseous products cotaining nitrogen varied regularly with reaction temperature and time. It was found that only phenols gave the gas rich in NO and that the behavior of gaseous productsevolved in the oxidation of o-cresol was so similar to it on the cases of the coals. It is possible to conclude from the results given above that in the processof humic acid formation from low rank coal by HNO₃-oxidation, phnolic structure in coal molecule might be destroyed.
In the oxidation of II in water under the initial O₂ pressure of 75 kg/cm² at 105°C, ammonium molybdate (Mo) accelerated the formation of humic acid selectively, while ammonium metavanadate (V) accelerated the entire oxidation rate unselectively. The oxidation rate of the coal decreased in CH₃COOH medium and molecular weight of humic acid obtained in this reaction was larger than that in water. From the results of decomposi-tion of H₂O₂ and oxidative destruction of pyrogallol, it was presumed that V had strong activities in the destruction of phenolic structure as well as the decomposition of in coal molecule whereas Mo had a slight activity in former and that the destruction and production of phenolic structure in coal molecule might be inhibited in CH₃COOH medium. It was therefore suggested that in O₂-oxidation humicacid was also produced after destruction of phenolic structure in coal molecule.

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he structure of picene derivative previously isolated from Yabari bituminous coal has been established by comparing with synthetic 2. 9-dimethyl-picene.
Chrsene derivative isolated from Yubari bituminous coal was identified by analysis, ultraviolet and infrared absorption spectra, conversion to the 2, 4, 7-trinitrofluorenone complex.
It was recognized that these two materials were identified to 2. 9-dimethylpicene and 1, 2, 3, 4-tetrahydro 2, 2. 9-trimethylpicene respectively.
The probable formation of these materials are discussed.

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The benzene-soluble fraction of brown coal depolymerized in phenol with p-toluene sulphonic acid as catalyst was methylated and fractionated by liquid chromatography. 2-(4-methoxyphenyl)-benzofuran, 9-(4-methoxyphenyl)-xanthene, 9-(2-methoxyphenyl)-xanthene and xanthone were identified, suggesting that the structures
-CH2-O=CH-, -CH=C-OH-, etc.
may exist in the brown coal.

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Seventeen kinds of vitrains in different ranks were immersed in ethylene diamine at room temperature and variation of ESR absorption spectra was examined. Absorption intensity increases in the cases of brown coals and anthracite while it decreases in the cases of bituminous coals. Degree of the variation seemed to be in close connection with the rank of coals. It was also observed that in ethylene diamine the line width at half height and the peak-to-peak line width were smaller and that saturation took place more easily than in air or in vacuum. The variations of ESR spectra caused by ethylene diamine were reversible by wash with methanol. In ethylene diamine some kinds of bituminous coals showed a composite ESR signal and the variation of line shape was also reversible. Considering with the effects of the other solvents and reagents on ESR spectra, it is considered that the increase in intensity observed in the cases of brown coals originates from formation of semiquinone type anion radicals and that the variations for bituminos coals is explained with the assumptions that a part of localized spin centres forms a complex with ethylene diamine which has a radical masking effect and that the process is reversible.

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The reflectance of vitrinites of twelve Japanese and fine foreign coals were measured by photo-multiplier method and the relations between the reflctance and the values of various analyses were elucidated.
The reflectance of Japanese coals, as well as foreign coals, increased almost conti-nuously with coal rank.
The reflectance increased slightly with coal rank up to 86‰ C but abrupt above 86‰ C.
Optical anistropy was observed, for the coals above 86‰ C, and the higher the coal rank is, the greater the anisotropy increased.
In the range from 83‰ C to 86‰ C, the reflectance kept almost constant. This phenomenon correlatis with the fact that the coals ranging from 83‰ to 86‰ C contain much hydrogen and volatile matter as compared with their carbon content.
Structural analysis was carried out from the data obtained here and the values of various analyses, the rerults are:
1) In low raak coals (less than 80‰ C), aromatic cluster units are smoll, but gradually increase with coal rank.
2) Caking coals contain much aliphatic or alicyclic groups, though aromatic cluster units increase slightly with coal rank.
3) In coals more than 86‰C, aromatic cluster units are not only developed horizonfally but also piled up vertically with coal rank.

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The present studies were undertaken to make clear the composition and the pyrolysis properties of the bojuntan constituents closely related to some phsical and chemical properties of original bojuntan. Bojuntan was prepared from Miike coal and typical solvents of coal tar such as dehydrated tar anthracene oil free from crystalline anthracene and phenathrene, etc., or pitch oil. The volatile components, the solvent extracts and their residues from the bojuntan, or their pyrolysis products at 400-600°C were examined by programmed temperature gaschromatography. The volatile component was composed of many aromatic compounds, of which boiling points ranged from that of naphthalene to pyrene, and the main constituents were anthracene (most abundant one), fluoranthene, pyrene, etc. The pyrolysis products of the benzene extraction residue was mainly composed of highly volatile compounds unidentified and aromatic compounds, of which boiling point ranged from that of benzene to pyrene. The pyrolysis product of the resin, soluble in benzene and insoluble in methanol, was composed of highly volatile compounds unidentified and rather small amount of aromatic compounds, of which boiling points ranged from that of benzene to naphthlene. The amount of each aromatic compound in those pyrolysis product was varied by different conditions of the pyrolyis and of the preparation of bojuntan.
The appearance of those aromatic compounds suggests the presence of certain labile aromatic groups in the structure of the solvent extraction residue and the resin. The properties observed on the gaschromatogram, therefore, might have certain relations with the other chemical and physical properties of the constituents, and also with those of bojuntan.

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Yubari coal was hydrogenated under 220-230 kg/cm² hydrogen pressure at 400°C and 450°C with red mud as catalyst. The nominal reaction time was changed from 0 to 120 min. No oil vehicle was used. The reaction product was frac-tionated by n-hexane and benzene into five fractions (Fig. 1) and the yield of each fraction was determined. The structural parameters of each fraction of the hydrogenated products were calculated from the contents of the different types of hydrogen measured by high resolution NMR spectroscopy (60 Mc) and from the elemental composition of each fraction. In the preceding reaction, from the change of yield of these fractions, the change of respective structural parameters of the mean structural unit, and the change in mean molecular weight measured by vapor pressure osmometer, the mechanism of the hydrogenolysis of coal under these experimental conditions was surmized to be as follows,
(1) While part of the coal was converted directly into oil-1 (including gas and water), the main process of coal hydrogenolysis can be described by the following reac-tion scheme,
coal→ asphaltene → oil-2 → oil-1 (including gas and water).
The main chemical reactions occuring during coal hydrogenolysis were assumed to be, (2) At 400°C: destruction of bridges between unit structures and dealkylation in the unit.
(3) At 450°C: destruction of bridges between unit structures, dealkylation in the unit, and hydrocracking of the aromatic ring.
The mean structural unit of asphaltene obtained from Yubari coal hydrogenated products appeared to be 3 or 4 condensed aromatic rings, and it showed a form ranging from dimer to tetramer.

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