110 TIDESWELL AND WHEELER BANDED BITUMINOUS COAL. XIX-Banded Bituminous Coal. Studies in the Composition of Coal. By FREDERICK VINCENT TIDESWELL and RICHARD VERKON WHEELER. As the result of an investigation into the chemical nature of the ingredients of banded bituminous coal (J. 1919 115 619) it was found that the chief differences between them were expressed by a regular gradation in composition and in properties which could be accounted for by assuming the occurrence in each in different proportions of “ reactive ” and ‘‘ inert ” types of compounds. We are now able to offer as the result of later work more particularly that on dopplerite (J. 1922 121 2345) an explanation as to the character of these presumed “ reactive ” and “ inert ” constituents. The various plant entities and residues that have contributed to the formation of the organic substance of coal can conveniently be grouped according as they are : (1) Resistant to decay.Amongst the more important members of this group are ( a ) Spore-exines and cuticular tissues; and ( b ) resins. The members of this group are either : ( a ) Organised such as cellulosic and lignified tissues; or ( b ) amor-phous the contents of plant cells. (2) Xubject to decay. (3) The products of decay. An accumulation of plant remains immediately after de-position consists mainly of the first two groups but in an older deposit such as a peat bed certain changes have taken place. The members of group 1 are still present in an apparently unaltered form. The cellulose and lignin of group 2 however have suffered decay undergoing such minor alterations as dehydration produces, or becoming ulmified (probably in conjunction with certain of the cell-contents) or disappearing altogether.According to Fischer and Schrader (Brennstofl Chem. 1921 2 23) the lignin alone sur-vives in any form the cellulose of necessity vanishing (being con-verted into liquid and gaseous products through the agency of bacteria) but we cannot regard this view as either proved or prob-able and consider that ulmins can be produced from any plant material of carbohydrate type. Judging from the nature of peat, ulmification is the main chemical process during the decay of plants and it proceeds further the older the deposit thus whilst a young peat may yield only 10 or 20% of material soluble in alkalis from an older peat as much as 70 or 80% can be extracted.In a deposit of the age of coal it cannot be expect,ed that the The ulmins STUDIES IN THE COMPOSITION OF COA4L. 111 materials of any of the three groups will remain unaltered. Spore-exines and cuticular tissues may not be much changed nor need the resins but the cellulose that is not totally destroyed will in large part be converted together with the more resistant lignin and part of the cell-contents into the amorphous ulmins of group 3 (or products derived from them). There will also be material corre-sponding with group 2 (a) consisting of altered (but apparently not ulmified) woody tissues such as compose many lignites and are recognisable in many bituminous coals.We have a t present no knowledge as to what becomes of the non-ulmified portions of the cell-contents. As they finally appear in the coal cell-wall structures group 2 (a) may not differ much chemically from the amorphous ulmins but the materials of group 1 differ markedly. The more recent beds of plant remains the peats contain a large amount of alkali-soluble material the amount increasing with the age of the deposit but ‘( older ” fuels such as brown coals and lignites contain comparatively little whilst bituminous coals, unless they have been considerably weathered usually contain none. This diminishing content of alkali-soluble material after a certain stage has been passed would seem to be due to a change in the character of the ulmins through condensation dehydration and loss of carboxyl (with the formation of anhydrides and lactones) whereby their usual property of dissolving in alkalis t o form dark brown solutions is lost.The alkali-soluble ulmins that surround and permeate the plant structures in an old peat (see J. 1922 12l, 2345) may be presumed to have their counterpart in bituminous coal in the amorphous cementing material (insoluble in alkalis) in which the numerous plant structures are embedded. We have already (Eoc. cit. p. 2354) instituteda comparison and shown the similarity between dopplerite a typical peat ulmin which occurs segregated in bands in some peat bogs and vitrain, the brilliant structureless ingredient of banded bituminous coal. By analogy there should also be a close relationship between all the amorphous cementing material of bituminous coal whether segregated as in a vitrain or diffused as in a clarain and a durain, and the amorphous ulmins that form so large a part of the older peats and this relationship should extend to the amounts of amor-phous material normally contained in the two fuels.The correctness of this suggestion can be deduced from the data obtained during the study of the chemical nature of the ingredients of banded bituminous coal referred to a t the beginning of this paper. The (‘ reactivity ” of the vitrain clarain and durain of Hamstead coal as measured by their susceptibility to attack by solvent 112 FRANCIS AND WHEELER THE OXIDATION OF and reagents and by the amounts of liquid and gaseous products yielded on destructive distillation was found to diminish in the ratio 1.0 0.9 0.7 taking the ingredients in the order named, and it was concluded that the amounts of “reactive” material they contained diminished in the same proportion.Of the absolute amounts of “ reactive ” and “ inert ” materials present in any one of the ingredients no conclusion could be drawn at the time the experiments were made but with the recognition of vitrain as related to the nearly homogeneous ulmin dopplerite it follows that the bulk of vitrain should be regarded as “ reactive.” Whence since its composition had been found to be similar in all three ingredients it must be concluded that the reactive material of a clarain and a durain is essentially an insoluble derivative of the ulmins and that in the clarain and durain of Hamstead coal it is present to the extent of about 90 and 70% respectively.Actually the vitrain contained a certain amount of material other than insoluble ulmins (resins for example) so that these figures should be reduced somewhat. It is difficult to judge from an examination of transparent sections of coal as to the proportions of amorphous and organised material present but even if as appeared there is in the Hamstead durain, for example a greater proportion of plant tissues than the 30% indicated by calculation there are grounds for the belief that some plant remains in coal (woody tissues in particular) although they retain their organised structures have been partially ulmified and thus function as “ reactive ” material.Otherwise the plant entities (especially those of group 1) must constitute what we have termed the “ inert ” material of coal. DEPARTMENT OF FUEL TECHNOLOGY, SHEFFIELD UNIVERSITY. [Received October 17th 1924. 110 TIDESWELL AND WHEELER BANDED BITUMINOUS COAL. XIX-Banded Bituminous Coal. Studies in the Composition of Coal. By FREDERICK VINCENT TIDESWELL and RICHARD VERKON WHEELER. As the result of an investigation into the chemical nature of the ingredients of banded bituminous coal (J. 1919 115 619) it was found that the chief differences between them were expressed by a regular gradation in composition and in properties which could be accounted for by assuming the occurrence in each in different proportions of “ reactive ” and ‘‘ inert ” types of compounds.We are now able to offer as the result of later work more particularly that on dopplerite (J. 1922 121 2345) an explanation as to the character of these presumed “ reactive ” and “ inert ” constituents. The various plant entities and residues that have contributed to the formation of the organic substance of coal can conveniently be grouped according as they are : (1) Resistant to decay. Amongst the more important members of this group are ( a ) Spore-exines and cuticular tissues; and ( b ) resins. The members of this group are either : ( a ) Organised such as cellulosic and lignified tissues; or ( b ) amor-phous the contents of plant cells. (2) Xubject to decay. (3) The products of decay. An accumulation of plant remains immediately after de-position consists mainly of the first two groups but in an older deposit such as a peat bed certain changes have taken place.The members of group 1 are still present in an apparently unaltered form. The cellulose and lignin of group 2 however have suffered decay undergoing such minor alterations as dehydration produces, or becoming ulmified (probably in conjunction with certain of the cell-contents) or disappearing altogether. According to Fischer and Schrader (Brennstofl Chem. 1921 2 23) the lignin alone sur-vives in any form the cellulose of necessity vanishing (being con-verted into liquid and gaseous products through the agency of bacteria) but we cannot regard this view as either proved or prob-able and consider that ulmins can be produced from any plant material of carbohydrate type.Judging from the nature of peat, ulmification is the main chemical process during the decay of plants and it proceeds further the older the deposit thus whilst a young peat may yield only 10 or 20% of material soluble in alkalis from an older peat as much as 70 or 80% can be extracted. In a deposit of the age of coal it cannot be expect,ed that the The ulmins STUDIES IN THE COMPOSITION OF COA4L. 111 materials of any of the three groups will remain unaltered. Spore-exines and cuticular tissues may not be much changed nor need the resins but the cellulose that is not totally destroyed will in large part be converted together with the more resistant lignin and part of the cell-contents into the amorphous ulmins of group 3 (or products derived from them).There will also be material corre-sponding with group 2 (a) consisting of altered (but apparently not ulmified) woody tissues such as compose many lignites and are recognisable in many bituminous coals. We have a t present no knowledge as to what becomes of the non-ulmified portions of the cell-contents. As they finally appear in the coal cell-wall structures group 2 (a) may not differ much chemically from the amorphous ulmins but the materials of group 1 differ markedly. The more recent beds of plant remains the peats contain a large amount of alkali-soluble material the amount increasing with the age of the deposit but ‘( older ” fuels such as brown coals and lignites contain comparatively little whilst bituminous coals, unless they have been considerably weathered usually contain none.This diminishing content of alkali-soluble material after a certain stage has been passed would seem to be due to a change in the character of the ulmins through condensation dehydration and loss of carboxyl (with the formation of anhydrides and lactones) whereby their usual property of dissolving in alkalis t o form dark brown solutions is lost. The alkali-soluble ulmins that surround and permeate the plant structures in an old peat (see J. 1922 12l, 2345) may be presumed to have their counterpart in bituminous coal in the amorphous cementing material (insoluble in alkalis) in which the numerous plant structures are embedded. We have already (Eoc. cit. p. 2354) instituteda comparison and shown the similarity between dopplerite a typical peat ulmin which occurs segregated in bands in some peat bogs and vitrain, the brilliant structureless ingredient of banded bituminous coal.By analogy there should also be a close relationship between all the amorphous cementing material of bituminous coal whether segregated as in a vitrain or diffused as in a clarain and a durain, and the amorphous ulmins that form so large a part of the older peats and this relationship should extend to the amounts of amor-phous material normally contained in the two fuels. The correctness of this suggestion can be deduced from the data obtained during the study of the chemical nature of the ingredients of banded bituminous coal referred to a t the beginning of this paper.The (‘ reactivity ” of the vitrain clarain and durain of Hamstead coal as measured by their susceptibility to attack by solvent 112 FRANCIS AND WHEELER THE OXIDATION OF and reagents and by the amounts of liquid and gaseous products yielded on destructive distillation was found to diminish in the ratio 1.0 0.9 0.7 taking the ingredients in the order named, and it was concluded that the amounts of “reactive” material they contained diminished in the same proportion. Of the absolute amounts of “ reactive ” and “ inert ” materials present in any one of the ingredients no conclusion could be drawn at the time the experiments were made but with the recognition of vitrain as related to the nearly homogeneous ulmin dopplerite it follows that the bulk of vitrain should be regarded as “ reactive.” Whence since its composition had been found to be similar in all three ingredients it must be concluded that the reactive material of a clarain and a durain is essentially an insoluble derivative of the ulmins and that in the clarain and durain of Hamstead coal it is present to the extent of about 90 and 70% respectively.Actually the vitrain contained a certain amount of material other than insoluble ulmins (resins for example) so that these figures should be reduced somewhat. It is difficult to judge from an examination of transparent sections of coal as to the proportions of amorphous and organised material present but even if as appeared there is in the Hamstead durain, for example a greater proportion of plant tissues than the 30% indicated by calculation there are grounds for the belief that some plant remains in coal (woody tissues in particular) although they retain their organised structures have been partially ulmified and thus function as “ reactive ” material. Otherwise the plant entities (especially those of group 1) must constitute what we have termed the “ inert ” material of coal. DEPARTMENT OF FUEL TECHNOLOGY, SHEFFIELD UNIVERSITY. [Received October 17th 1924.