Chemical Determination of Tetrahedral Ions in Nontronite and Montmorillonite

Abstract

Samples of nontronite and montmorillonite were digested with dilute hydrochloric acid for various periods of time. Cllemical determinations of the acid-soluble ions were made for each period of digestion. Curves are presented showing the rates of solution of these minerals ;as decreasing exponential functions of time. A change in the slopes of the curves, as plotted on semilogarithmic paper against time on the linear scale, suggests different rates of solution for the ions in the tetrahedral and octahedral layers. The initial slope of the curves represents the simultaneous rates of solution of the octahedral and tetrahedral layers with the octahedral layer predominating. The second slope of the curves represents the rate of solution of the tetrahedral layer predominantly. Extrapolation of this slope to zero time is thought to give the percent of the tetrahedrally substituted ions within very close limits. Solubility curves of nontronite suggest the presence of both iron and aluminum in the tetrahedral layer. The solubility curves for Polkville montmorillonite indicate there is no substitution for silicon in the tetrahedral layer. Experimental values of tetrahedral substitution in nontronite check very closely with values postulated from the theoretical calculations obtained from the chemical analysis of the mineral.

Kinetics of Acid-Dissolution of Palygorskite (Attapulgite) and Sepiolite

“…This break-up of the palygorskite is reflected by an increase in the slopes of the dissolution curves. As the slopes for the tetrahedral cations are lower than their corresponding octahedral cations as reported by Brindley and Youell (1951) and by Osthaus (1954), no evidence was obtained to suggest the presence oftetrahedral Al and Fe.…”

“…More detailed studies of the kinetics of acid dissolution were made by Osthaus (1954Osthaus ( , 1956. He digested several montmorillonites and a nontronite with HCI at constant temperatures for various periods of time.…”

Infrared spectra of muscovites as affected by chemical composition, heating and particle size

“…This could also explain why the 848 cm-1 band was eliminated but the 818 cm-1 band of Fe~+-OH was scarcely affected when nontronite was treated with hydrazine vapour in Farmer & Russell's experiments (1964). The existence of Fe in tetrahedral sites has been in fact shown by selective dissolution analysis (Osthaus, 1954), and by M6ssbauer spectral studies (Goodman et al, 1976). The recognition of tetrahedral Fe 3 + in sheet silicate would necessitate a reconsideration of the related spectral interpretations.…”

Dissolution of Smectites in Hydrochloric Acid: II. Dissolution Rate as a Function of Crystallochemical Composition

“…This is a linear dependence until E remains constant and thus the value t05 may be read for the temperature of 96~ as it is shown in Figure 1 Turner (1964) using the analytical data of Osthaus (1954Osthaus ( , 1956 and Turner (1964).…”

“…The kinetics and mechanism of dissolution of smecrites in HCI have been described by various authors such as Brindley and Youell (1951), Kar~ulin and Stubi6an (1954), Osthaus (1954Osthaus ( , 1956), Packter (1955), Granquist and Gardner-Sumner (1959), Fahn (1963), Turner (1964), Ci6el et al (1965), and many others.…”