Interaction of halogens and alkaline-earth elements in H2+O2+N2 flames

Abstract

By observing the effect of halogens on the resonance emission lines of the alkaline-earth elements in hydrogen + oxygen + nitrogen flames, it has been established that the great bulk of such elements becomes combined as gaseous mono and dihalides. It has not been possible to identify the nature of the monohalide formed but it has been established that no single monohalide is predominant and that the diatomic halides, MX, apparent in the flame emission, are of minor importance. The latter finding explains satisfactorily the previous discrepancy between flame and mass spectrometric determinations of D₀(MX). It has been verified that the predominant dihalide formed in these flames is the normal MX₂. Values for D₀(MX₂), the heat of atomization, were 211.1 kcal mol^–1 for CaCl₂; 209.1, SrCl₂; 217.9 BaCl₂ and 190.1 CaBr₂ all ±5 kcal mol^–1. The dichloride values are in excellent agreement with a recent mass spectrometric investigation and with recalculated thermochemical cycle values.