The Dehydration of Polyhalite

Abstract

The kinetics of the reaction KzCazMg(SO&.2Hz0 .-f K2CaMg(S0& + CaSOa -I-2H20 was studied by an iso-Differential thermal Below about 1.5 bars Between 1.7 and 6.1 bars, the results can be expressed as thermal method. analysis was used to determine the decomposition pressures between 0.5 and 6.1 bars. the reliability of the measurements is questionable. log P H~~ = 27.77 -1.75 X 104/T.The reaction is first order with log k (min.-I) = 21.50 -1.22 X IO4/?".

Deformation recorded in polyhalite from evaporite detachments revealed by 40Ar/39Ar dating

“…Polyhalite is known to dehydrate with the following first order reaction between 280˚ to 360˚ at pressures between 0.5 and 6.1 bars from heating experiments (Nathans, 1963). Further, thermal experimentation by Wollmann et al (2008) identified the dehydration characteristics of polyhalite and its analogues with dehydration onset at 255 ˚C and peaking at 343˚ ˚C for polyhalite and onset between 185 -311 ˚C for the various analogues.…”

Deformation recorded in polyhalite from evaporite detachments revealed by 40Ar ∕ 39Ar dating

“…Polyhalite is known to dehydrate with the following firstorder reaction between 280 and 360 • C at pressures between L. Richards et al: Polyhalite deformation and argon diffusion 0.5 and 6.1 bars from heating experiments (Nathans, 1963).…”

Fourier projections of unpaired electron densities

“…There is lio nl~gzmtic nionlcnfl residing on the A1 atoms. Measurement of magnetic structure factors using polarized neutrons has been amply described elsewhere (Nathans, Shull, Shirane & Andresen, 1959;Nathans, 1960). The interest here is in pointing out for the projection in 5(a).…”

“…Another consequence is the sensitivity of the measurements to the valence electron configuration, which, although representing a small perturbation of the spherical symmetry of the total ~l~troa cloud, is ~iagl~4 out by the n~u~ron magnetic scattering process. Secondly, at least as far as polarized neutron measurements are concerned, the magnetic amplitude is determined relative to the nuclear in phase as well as magnitude (Nathans, 1960). This fact, though limiting the present application of such measurements to known structures, eliminates the ambiguity in sign of the coefficients in the synthesis.…”