Über die Struktur und die Eigenschaften synthetischer Montmorillonite

Karšulin, Miroslav; Stubičan, Vl.

doi:10.1007/bf00904000

Cited by 10 publications

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“…Brindley and Youell (1951) were the first to attempt the direct chemical determination of octahedral and of tetrahedral aluminum in layer silicates by an acid-dissolution technique. Karsulin and Stubican (1954) also applied the same method to several synthetic montmorillonites and experimentally determined the amounts of aluminum in octahedral and in tetrahedral coordination.…”

Section: Introductionmentioning

confidence: 99%

Kinetic Studies on Montmorillonites and Nontronite by the Acid-Dissolution Technique

Osthaus

1955

Clays clay miner. (Natl. Conf. Clays Clay Miner.)

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Several montmorillonites and a nontronite were digested in hydrochloric acid at constant temperature for various periods of time. Soluble iron, aluminum, magnesium, and in two samples titanimn, were determined for each digestion period. Rate of solution curves were obtained by plotting the logarithm of the percent of the residual ions against time. In general, the solution curves were straight lines or curves that could be resolved into two straight lines. From the interpretation of the dissolution curves, it was possible to determine the amount of the ions in octahedral and tetrahedral coordination. For some of the samples, the rate curves also gave the amount of iron and/or aluminum extraneous to the clay lattice. The amount of silicon in the clay lattice was calculated using the experimentally determined octa, hedral cations, substituted tetrahedral cations if any, and the exchangeable cations assuming 44 charges per unit cell. The distribution of cations in lattice layers indicates that the eight montmorillonites are substantially dioctahcdral. Two of the samples showed the presence of iron in tetrahedral coordination while all the samples showed extraneous silicon. The presence of extraneous silicon, iron, and aluminum in purified samples indicates that formulas derived from bulk chemical analyses can be inaccurate. The dissolution of the ions from the clay lattice determined at several different temperatures in one sample and at two acid concentrations in another sample is in agreement with chemical kinetic principles and is a first-order reaction. The rate constant for the acid dissolution reaction increased proportionately with the acid concentration. The activation energies were determined for the solution of iron and aluminum in montmorillonite from Polkville, Mississippi, and nontronite from Garfield, Washington, using Arrhenius' Law. In both samples the activation energies (17 to 18 kilocalories per mole) were the same. In the nontronite sample the activation energies were identical for what have been interpreted as octahedral and tetrahedral ions.

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Section: Introductionmentioning

confidence: 99%