Replacement of nickelhexahydrite with retgersite: Polymorphic-metasomatic structures

Abstract

The polymorphous transition that occurs during the process of metasomatic replacement was observed in the experiment on the retgersite paramorph formation after nickelhexahydrite crystals. This process runs through a solution film formed on the primary crystal surface and then penetrated into the crystal along with the replacement front. One or several secondary mineral grains have ingrown into a comparatively perfect crystal up to the complete replacement; these grains are randomly oriented with regard to the crystal. A finegrained mass replaces the imperfect crystals. An aggregate of mineral grains incorporated into the fine-grained mass is an intermediate case. Single-crystal pseudomorphs have been synthesized for the first time as products of the nonisomorphic interaction. Conditions of the nickelhexahydrite metastable equilibrium and the retgersite stable equilibrium are closely related and determine the structural features of the replacement reactions for these two compounds. A relatively low supersaturation with retgersite in the vicinity of the eutonic point resulted in the nucleation and growth of secondary single crystals. A deviation from the eutonic point gives rise to the increasing supersaturation and mass precipitation of the secondary phase.

Some properties of aqueous solutions of α-NiSO4 · 6H2O

“…Similar results were obtained for retgersite solu tions in 20% H 2 SO 4 at 27°С. In this case, the partial densities were (with a linear approximation error of 0.002 g/cm 3 ) as follows: d solv = 1.125 ± 0.002 g/cm 3 d salt = 2.31 ± 0.03 g/cm 3 .…”

“…1) with approximation errors of 0.003 and 0.007 g/cm 3 for 22.8 and 35.5°С, respectively, indicates the constancy of partial densities in the entire concentration range under study. The partial values were found to be at 22.8°С d solv = 1.001 ± 0.003 g/cm 3 d salt = 2.31 ± 0.03 g/cm 3 at 35.5°С d solv = 1.001 ± 0.007 g/cm 3 d salt = 2.24 ± 0.06 g/cm 3 . Similar results were obtained for retgersite solu tions in 20% H 2 SO 4 at 27°С.…”

“…Their growth is met by a number of difficulties which are caused, on the one hand, by the presence of nickel sulfates with a dif ferent content of crystallization water [2,3] and, on the other hand, the tendency to narrow the light trans mission band.…”

The Effect of Reaction Conditions and Presence of Magnesium on the Crystallization of Nickel Sulfate

“…Particle properties such as size, size distribution and shape effect their filterability, and thus should be controlled if possible [25]. [15,24]. Solubility curves in both studies show two eutonic points, A and B, representing the tion points for the thermodynamically most stable phase.…”

“…Crystallization experiments were performed using a 100 mL temperature-con double-walled batch reactor (Figure 2), as described in detail in our previous wor [15,24]. Solubility curves in both studies show two eutonic points, A and B, representing the transition points for the thermodynamically most stable phase.…”