Structure of Carboxyl Groups in Humic Acids

Abstract

IN a recent communication¹ we reported that four moles of water were evolved to one mole of carbon dioxide when humic acids, derived from a North Dakota lignite, were decarboxylated at 150° in a stream of dry nitrogen. It was suggested that some of the acid function of the humic acids was in the ionized form, —COO−H₃O+·3H₂O, although it was noted that relatively weak solid acids were not expected to be readily ionized. At the time the original experiments were carried out, infrared spectra of potassium bromide pellets of the resultant humic acids which had been dehydrated and decarboxylated at 150° for 65 h were recorded on a Beckman IR-5 spectrophotometer. It is the purpose of this communication to compare the original spectra with those reported in the preceding communication by Falk and Smith.