thenardite


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Related to thenardite: Mirabilite

thenardite:

see sodium sulfatesodium sulfate,
chemical compound, Na2SO4. It is a white, orthorhombic crystalline compound at ordinary temperatures; above 100°C; it assumes a monoclinic structure, and above about 250°C; it assumes a hexagonal structure.
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Thenardite

 

(named for the French chemist L. J. Thénard, 1777–1857), a mineral of the sulfate class, Na2SO4. Thenardite contains small amounts of K, Mg, Cl, Br, H2O, and, as a component of a mechanical mixture, CaSO4. It crystallizes in the ortho-rhombic system, whereas its high-temperature polymorph, me-tathenardite, crystallizes in the hexagonal system. The structure consists of a framework of Na polyhedrons surrounded and interconnected by SO4 tetrahedrons. The colorless transparent crystals have a dipyramidal or tabular habit; cruciform twinning and perfect cleavage are characteristic features. Thenardite occurs most commonly in the form of milky white granular aggregates. It is freely soluble in water and has a bitter, salty taste. Hardness on Mohs’ scale is 2–3, and the density is 2,680–2,690 kg/m3.

Thenardite is a chemogenic mineral formed, together with mi-rabilite, epsomite, and gypsum, in evaporating salt lakes; it is also formed upon dehydration of mirabilite. It precipitates from supersaturated solutions at temperatures above 32.4°C; in the presence of NaCl, however, it may crystallize at temperatures as low as 13.5°C. The mineral is also known as a product of fumar-ole activity.

There are thenardite deposits in, among other places, the USSR (Kara-Bogaz-Gol in the Turkmen SSR, the Mormyshan-skie lakes in the Kulunda Steppe in northeastern Kazakhstan), the United States (borax and alkali lakes in California and Nevada), and Canada. Thenardite is primarily used as raw material in the sodium-carbonate industry and in glassmaking.

thenardite

[thə′när‚dīt]
(mineralogy)
Na2SO4 A colorless, grayish-white, yellowish, yellow-brown, or reddish, orthorhombic mineral consisting of sodium sulfate.
References in periodicals archive ?
In order to investigate the possible crystallization process of thenardite by increasing the calcining temperature, XRD analyses were carried out on the samples calcined at 200[degrees]C, 400[degrees]C, and 600[degrees]C, respectively.
The crystal structure of thenardite is shown in Figure 2.
Thenardite belongs to [F.sub.ddd] space group with octahedral structure of nearly regular S[O.sub.4] tetrahedra and distorted Na[O.sub.6] octahedra.
Due to the lower lattice energy, [Na.sub.2]S[O.sub.4] nucleates in thenardite form predominantly in solution phase attributed to thermodynamic constraints.
The SEM picture of as-prepared thenardite is shown in Figure 3.
All the thenardite crystals are distributed uniformly.
Figure 4 gives the IR spectra of thenardite calcined at different temperature in the range of 400-4000 [cm.sup.-1].
The TSL glow curves of thenardite sample were recorded at RT for different [gamma]-ray irradiation from 0.25 to 4 kGy (Figure 6).
However, it is suggested that the irradiation of thenardite phosphor at high doses results in the formation of deep traps which resulted in the fading of TL signal.
The trap parameters, such as activation energy and order of kinetics, were calculated for the 430 K glow peak of the thenardite phosphor irradiated with a gamma dose of 2 kGy at RT using the Chen's set of empirical formulae for the shape of the glow curve [24].