[stansfield] carbonization OF LIGNITES 129 



Appendix I. 



Weathering of Carbonized Lignite 



By E. Stansfield, M.Sc; R. E. Gilmore, M.Sc; 

 J. H. H. NicoLLS, M.Sc. 



In an earlier report' it was stated that carbonized lignite changed 

 notably on exposure to air, and this matter has since been further 

 investigated. 



Samples exposed to air over sulphuric acid in a desiccator, for 

 periods of up to one year, showed gains in weight averaging 3.4%, 

 although one isolated case of over 6% was observed. The calorific 

 value, corrected to the original weight, showed an average decrease 

 of 1-9%; the apparent drop in calorific value averaging 5-1%. 



A sample exposed for three days to oxygen under a pressure of 

 about 25 atmospheres, showed a gain in weight of 12-4%. Exposure 

 in a repeatedly evacuated desiccator reduced this gain to 4-3%, 

 but the drop in calorific value, corrected to the original weight, was 

 almost negligible. 



A sample of lignite, carbonized after its mineral impurities had 

 been largely removed by treatment with hydrochloric and hydro- 

 fluoric acids, showed gains in weight which at first appeared to be 

 normal, but later slowed off and fell below the average. 



Dry air, enclosed over mercury in a tube containing a sample 

 of lignite which had been carbonized in an evacuated retort, was 

 rapidly absorbed at first, but more slowly later. After 4}^ months 

 the total absorption amounted to about 25% of the volume of the 

 air, corresponding to 1-7% of the weight of the lignite residue. This 

 residual gas contained no carbon dioxide, and only 0-07% of oxygen. 



The following conclusions have been drawn. The carbonized 

 lignite rapidly occludes oxygen and, possibly to a less extent, nitrogen; 

 the occluded oxygen then gradually oxidises the material, with a 

 corresponding slow reduction of the calorific value. The oxidation 

 does not appear to be confined to the mineral impurities. 



iThe Carbonization of Lignites, Trans. R.S.C. Series III (1917) Vol. XI p. 90. 



