Visible Spectra of Thin Sections and Polynuclear Condensed Aromaticity of Pittsburgh Coal Vitrain

Abstract

LIMITS on polynuclear condensed aromatic contents have been determined by ultra-violet-visible spectra of ground thin sections^1,2 and microtomed ultra-thin sections^3,4. The visible spectrum of ground sections has been rechecked on thick sections for which accurate measurements of thickness were possible. The spectrum obtained for a 10.3µ, hole-free section is curve D of Fig. 1; the spectral region below 5000 Å is not accessible with sections of this thickness. The previously published composite spectrum² for six sections varying in thickness from 2 to 10µ is curve C. Curve A, a portion of the published spectrum of a microtomed section 550 Å thick^3,4, shows K values greater than those of curve D by factors from 7.8 at 6400 Å to 4.3 at 5000 Å. The content of condensed polynuclear aromatics allowed by curve D in this spectral region would be smaller by similar factors.