Solubility of Sodium Tungstate

The heat of formation of sodium tungstate has been found to be:

Na2O + WO3 = Na2WO4 + 94,700 calories.

The aqueous solution, which is alkaline, when allowed to crystallise at temperatures above 6° C., yields slender nacreous crystals of the dihydrate, Na2WO4.2H2O, in the form of rhombic bipyramidal scales, a:b:c = 0.8002:1:0.6470, of density 3.259 at 17.5° C. and 3.231 at 19° C. This hydrate is stable in the air, and it is in this form that the salt is generally used. When heated, it loses water at 200° C., becomes opaque, and finally melts. It dissolves readily in hot water, but may be precipitated by means of alcohol. The solution yields white tungstic acid on the addition of mineral acids.

If the aqueous solution is allowed to crystallise at temperatures below 6℃, the decahydrate,Na2WO4·10H2O, is obtained.

The solubility of sodium tungstate has been determined by Funk as follows:

Solid Phase Na2WO4.10H2O.
Temperature,° C.	Grams Na2WO4 in 100 Grams Solution.
-5	30.60
-4	31.87
-3.5	32.98
-2	34.52
0	36.54
+3	39.20
+5	41.02

Solid Phase Na2WO4.2H2O.
Temperature,° C.	Grams Na2WO4 in 100 Grams Solution.
-3.5	41.67
+0.5	41.73
+21	42.27
+43.5	43.98
+80.5	47.65
+100	49.31

These results are shown graphically in fig.

Binary Systems Na2WO4 - Na2SiO3 and Na2WO4 - K2WO4

The anhydrous normal tungstate, Na2WO4, is prepared by the fusion method described for potassium tungstate, or by complete dehydration of the hydrates at 100° C. or over sulphuric acid. It may be obtained from the mineral wolframite by fusion with alkali as already described.

The anhydrous salt exists as white crystals, of density 4.1833 at 18.5° C. and 4.1743 at 20.5° C., which melt at 698° C. On heating it undergoes two transformations, the first with considerable development of heat, and finally boils. The transition temperatures between the polymorphic forms thus indicated have been determined from the cooling and heating curves as follows:

Method	Transition Point ° C		Melting point of β Form
	δ⇔γ	γ⇔β
Cooling curve	570	. . .	698
Cooling curve	564	588	698
Cooling curve	568	585	698
Cooling curve	572	589	700
Heating curve	587	591	694

The binary systems Na2WO4 - Na2SiO3 and Na2WO4 - K2WO4, and the properties of aqueous solutions of the mixtures, have been investigated.

Sodium Tungstate Applications

Sodium Tungstate has applications as a catalyst, analytical reagent, fire proofing agent. It features a high degree of chemical purity and outstanding water solubility with no residue. It can be used in the manufacture of metal tungsten, tungsten acid, tungsten salts, and dyes, galvanic coatings, and the manufacture of X-ray contrast agents.

Sodium tungstate is Colorless or white crystalline powder and widely used as catalyst in paint industries, dyes industries, pigments and pharmaceuticals and many more chemical reactions like epoxidation of alkenes and oxidation of alcohols into aldehydes or ketones, it also used in Manufacture of heteropolyacid color lakes used in printing inks, plants, waxes, glasses, and textiles, Analytical reagent, Reagent for alkaloids, uric acid and plasma proteins, Fuel-cell electrode material, and Fire proofing agent, Manufacture of metal tungsten, tungstic acid and tungsten salts.

Sodium tungstate is an effective Antidiabetic agent when administered orally. It improves pancreatic function and beta cell proliferation. It activates glycogen synthesis through an insulin receptor-independent pathway.

There are dual effects of sodium tungstate on adipocyte biology: inhibition of Adipogenesis and stimulation of cellular oxygen consumption. Sodium tungstate inhibits adipocyte differentiation and regulates the mitochondrial oxygen consumption of adipose cells. These effects contribute to the anti-obesity activity of sodium tungstate and confirm its potential as a powerful alternative for the treatment of obesity.

Sodium tungstate is used for slurry sampling electro thermal atomic absorption spectrometric determination of indium in soils.

Typical applications include catalysis, pigment production, galvanic coatings, and the manufacture of X-ray contrast agents.

Calcium Tungstate Applications

Calcium tungstate is a very important chemical materials, which has applications in mainly ways:

1. For production of ammonium paratungstate, tungsten trioxide, tungsten iron, steel, carbide, tungsten materials, tungsten and tungsten alloys and other tungsten products;

2. Used as raw materials of tungsten series chemical products;

3. For fluorescent paint, photography screen pipe, medicine, X-ray photograph and fluorescent lighting;

4. Calcium tungstate is also used for luminous paint, fluorescent lights, neon lights, X-rays screen, medicine, scintillation counter and lasers.

Calcium Tungstate Advantages

The interest in CaWO4 and CaMoO4 has been driven by the fact that these compounds have especially attractive properties for a variety of optical applications (phosphors, laser hosts, scintillators).

Recently, CaWO4 was implemented in the CRESST dark matter search, enabling discrimination between electron and nuclei recoils. Different types of interaction events can be identified by simultaneously measuring a combination of phonon and scintillation signals from cryogenic phonon-scintillation detectors (CPSD) operating at milli-kelvin temperatures. This technique offers high sensitivity and the unique advantage of background identification, which is crucially important for experimental searches for rare events.

Calcium Tungstate Manufacturing Process

The following methods is for calcium tungstate manufacturing process:

1.Mix sodium tungstate and sodium sulfide and dissolve into water, then add zinc chloride aqueous solution. After filtration, treat filtrate with calcium chloride, and then we can get calcium tungstate.

2.Calcium oxide/calcium hydroxide reacts with tungsten oxide/tungsten tetrahydroxide in alkali hydroxide/carbonate solution, and then calcium tungstate is obtained.

3.Burning tungsten trioxide and calcium carbonate in 1070℃ or treatment between sodium tungstate solution and calcium chloride solution or processing scheelite.

Calcium Tungstate

Calcium tungstate is white powder with tetragonal structure. Its relative density is 6.062. Slightly soluble in water and ammonium chloride solution. Dissociation in hydrochloric. Calcium tungstate is a very important chemical materials, mainly used for production of ammonium paratungstate, tungsten trioxide, tungsten iron, steel, carbide, tungsten materials, tungsten and tungsten alloys and other tungsten products.

Calcium Tungstate is generally immediately available in most volumes. High purity, submicron and nanopowder forms may be considered. American Elements produces to many standard grades when applicable, including Mil Spec (military grade); ACS, Reagent and Technical Grade; Food, Agricultural and Pharmaceutical Grade; Optical Grade, USP and EP/BP (European Pharmacopoeia/British Pharmacopoeia) and follows applicable ASTM testing standards. Typical and custom packaging is available. Additional technical, research and safety (MSDS) information is available as is a Reference Calculator for converting relevant units of measurement.