The composition of humic substances isolated from mongolian brown coal

Methods of elemental analysis, gel-filtration, potentiometry, IR and UV spectroscopy and also 13C NMR were used to study the specific structural features of humic substances separated from low-metamorphized low-calorie brown coal and its residue left after the separation of free humic substances and oxidized by a solution of nitric acid. Treatment of brown coal with nitric acid (15%) leads to an increase in the yield of humics, a change in the content of functional groups and also to the degradation and nitration of the macromolecules. © 2006 by Allerton Press, Inc.