The Constituents of Banded Humic Coal. 175 
contrast to ' provitrit ') is, however, now known to be rare, 
if existent. When polished and etched surfaces of vitrain are 
examined by reflected light, most specimens show pseudo- 
morphs of plant cells. It is possible, by regulating the 
oxidation and removing the soluble ulmins by means of dilute 
sodium hydroxide, to see and photograph the more obvious 
structures, but the pseudomorphs disappear as the ulmins 
dissolve. The structures cannot be separated and retained as 
can (from durain, etc.) spore-cases, cuticles, fibres and 
tracheids. The only plant -residues in vitrain are rodlets of 
* resins. ’ 1 
(10) The adsorption of water vapour, in cases in which the 
oxygen content of a coal is less than 10 per cent., runs parallel 
to the oxygen content. 2 
(1 1 ) The deductions, shown in the Table, that vitrain, 
clarain and durain are mainly formed under water are 
generally, though not universally, accepted. 3 For example, 
Taylor observes, ‘ The roofs of the bituminous coal seams, 
ranging in age from the Carboniferous to recent, have 
two characteristics in common : (a) they are alkaline ; 
and ( b ) they contain replaceable sodium in excess of replace- 
able calcium. . . . Bacterial decomposition of vegetable 
matter can take place under such a roof, and results in the 
formation of solid reduction products, one of which is fusain/ 
(12) The oxidisability with dilute potassium perman- 
ganate cited is due to Kreulen. 4 
(13) The examples of figures obtained from destructive 
distillation of the ingredients are due to Greenwood. 5 
Amounts from the true sample of coal were : coke, 66.8 per 
cent. ; tar, 8.9 per cent. ; liquor, 7.5 per cent. ; gas, cc. per 
10 grm. 3,100. 
(14) The example of the amounts of oil obtained by 
hydrogenation is due to Shatwell and Graham. 6 
(15) Professor Hickling 7 has pointed out that vitrain and 
1 Hickling, H. G. A. and C. E. Marshall, ‘The Microstructure of the 
Coal in certain Fossil Trees,’ Trans. Inst. Mining Eng., Vol. LXXXIV, 
1932, p. 13. Seyler, C. A., Fuel, Vol. 5, 1926, p. 56. Stopes, M. C. 
and R. V. Wheeler, Fuel, Vol. 2, 1923, p. 122. 
2 Lea, F. M., Fuel, Vol. 7, 1928, p. 433. 
3 The following writers are in disagreement : — 
Stuart, M., ‘ The Geology of Oil, Oil-shale and Coal,’ London , 
1926, p. 21. Taylor, E. M., Fuel, Vol. 7, 1928, pp. 66-71, 127-134, 
327-8. Buchler, F., Gluckauf , Vol. 65, 1919, p. 161. 
4 Kreulen, D. J. W., Brennstoff-Chem., Vol. X, 1929, p. 397. 
5 Greenwood, H. D., ‘ Examination of the Banded Constituents of a 
Derbyshire Coal,’ Trans. Soc. Chem. Ind., Vol. 43, 1924, pp. 363-366. 
6 Shatwell, H. G., and J. I. Graham, ‘ Hydrogenation and Liquefac- 
tion of Coal,’ Fuel, Vol. 4, 1925, pp. 25-30. 
7 Hickling, H. G. A., ‘The Geological History of Coal,’ Fuel , 
Vol. 10, 1931, pp. 212-232. 
1933 August 1 
