Deuterium exchange during acid-demineralisation.

Isotopic analyses of residues prepared by demineralisation of the Murchison meteorite using D-labelled reagents provide evidence for measurable exchange of H-isotopes between residue and reagents. Precise quantification of this effect is precluded by substantial inhomogeneity of the meteoritic organic matter. A conservative estimate of the degree of exchange is 3 to 5% of the H pyrolysable as H2O. This could affect the shape of the curve defining D-release as a function of temperature, but does not change conclusions previously drawn concerning the nature of the bulk D-enrichment of insoluble organic matter in meteorites.