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The investigation of chemical structure of coal macerals via transmitted-light FT-IR microscopy by X. Sun

J.C. Hower·I. Suarez-Ruiz·Maria Mastalerz·A.C. Cook
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Abstract

A recent paper by Sun [X. Sun, Spectrochim. Acta A 62 (1-3) (2005) 557] attempts to characterize a variety of liptinite, termed "barkinite", from Chinese Permian coals. The component identified does not appear to fundamentally differ from previously-described liptinite macerals included in the International Committee for Coal and Organic Petrology's system of maceral nomenclature. Further, chemical comparisons made with macerals from coals of different rank and age are flawed because the author did not account for changes in chemistry with rank or for the chemical changes associated with botanical changes through geologic time. The author has not satisfactorily proved his hypothesis that the component differs morphologically or chemically from known liptinite-group macerals. ?? 2006 Elsevier B.V. All rights reserved.

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J.C. Hower, I. Suarez-Ruiz, Maria Mastalerz, A.C. Cook. 2007. The investigation of chemical structure of coal macerals via transmitted-light FT-IR microscopy by X. Sun. https://doi.org/10.1016/j.saa.2006.11.034

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Aqueous infrared carboxylate absorbances: Aliphatic di-acids

Aqueous attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectra of 18 aliphatic di-carboxylic acids are reported as a function of pH. The spectra show isosbestic points and intensity changes which indicate that Beer's law is obeyed, and peak frequencies lie within previously reported ranges for aqueous carboxylates and pure carboxylic acids. Intensity sharing from the symmetric carboxylate stretch is evident in many cases, so that bands which are nominally due to alkyl groups show increased intensity at higher pH. The asymmetric stretch of the HA − species is linearly related to the microscopic acidity constantof the H 2 A species, with σ p K <0.25 log units; this relationship falls on the same line as previously observed for mono-carboxylic acids. The linear relationship applies to the acidity constant of the HA − species only when the two acid groups are well separated (>2 intervening atoms). The results suggest that aqueous ATR-FTIR may be able to estimate `intrinsic' p K a values of carboxylic acids, in addition to providing quantitative estimates of ionization.

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