Small-angle neutron scattering study of coal extract solutions in pyridine

Three perdeutero-pyridine extracts of Illinois No. 6 coal were studied with SANS in an effort to: 1. check the reproducibility of the measurements; 2. check the reproducibility of the extractions; and 3. try to measure weight average molecular weights for the non-fractionated extracts. In addition one sample from the Bruceton mine of Pennsylvania was studied to check any dependence on the coal's origin and one silylated sample of an Illinois No. 6 extract was studied to assess the effect of chemical treatment of coals on the average molecular weight. The chemical composition and the number-average molecular weights were obtained for the same samples. Scattering data were observed to be well represented by the Debye theory for a random two phase system with an experimental density-density correlation function described by a correlation length a. The analysis of the data shows that the extraction is a non-reproducible operation and this seems to be due to the heterogeneous nature of coal. In addition the present methods available to obtain molecular weights from the scattering data do not seem to be applicable to coal extracts.