Infrared Study of the Thermal Decomposition of Ammonium Rectorite*

J. D. Russell and J. L. White
Department of Agronomy, Purdue University, Lafayette, Indiana
* This report is journal paper No. 2618 of the Purdue University Agricultural Experiment Station, Lafayette, Indiana.
On leave of absence from the Macaulay Institute for Soil Research, Aberdeen, Scotland.

Abstract: Changes in the infrared absorption spectrum of ammonium-saturated rectorite on heating suggest that the ammonium cations are hydrogen bonded to water molecules when the mineral is hydrated. Further spectral changes above 300°C indicate that lattice OH groups are perturbed by protons liberated from the decomposition of ammonium ions giving rise to an absorption doublet at 3500 and 3476 cm−1. The doublet attains maximal intensity when decomposition of ammonium cations and dehydroxylation of the mineral is complete at about 550°C.

The perturbation effect occurs only for swelling dioctahedral minerals which derive their layer charge from Al-for-Si substitution.

Clays and Clay Minerals; 1966 v. 14; no. 1; p. 181-191; DOI: 10.1346/CCMN.1966.0140115
© 1966, The Clay Minerals Society
Clay Minerals Society (www.clays.org)