29Si N.M.R. studies of aqueous silicate solutions

Abstract

Silicon-29 n.m.r. spectra have been obtained for a number of aqueous solutions of sodium and potassium metasilicate. The assignment of peaks to various silicate species is discussed. Linewidth and spin–lattice relaxation time measurements are reported as a function of ageing of the solutions in sealed glass tubes, and for solutions containing several paramagnetic additives (oxygen, Cr³⁺ and Mn²⁺). Silicon-29-{¹H} nuclear Overhauser measurements (NOE) were also made, and it is concluded that values of T₁ are markedly affected by paramagnetics, including some species leached from the glass of the tubes. The effect of using D₂O as solvent is also studied.