What is Sodium Tungstate?
Sodium tungstate is a critical inorganic compound, primarily valued as an intermediate in the production of tungsten and as a versatile reagent in both industrial and laboratory settings. While it exists in several forms, the dihydrate version is the most common commercial and laboratory form due to its stability and ease of handling. Tungsten, from which Sodium Tungstate is derived, is one of the densest and hardest metals on earth, with the highest melting point of any element. These extraordinary physical properties of tungsten translate into unique chemical characteristics for its compounds, including high thermal stability, catalytic activity, and corrosion-inhibiting ability.
Key Properties and Identification
Sodium tungstate exists in two primary commercial forms: Sodium Tungstate anhydrous and dihydrate. In most industrial and laboratory contexts, Sodium Tungstate Dihydrate is the most common and commercially traded product.
Properties of Sodium Tungstate Dihydrate:
- Compound name: Sodium Tungstate (Often referred to as Sodium Tungsten Dihydrate)
- Molecular Formula: Na₂WO₄·2H₂O
- CAS Number: 10213-10-2
- Molecular Weight: 329.85 g/mol Density: 3.25 g/cm³
- Appearance: White to off-white crystalline powder or granules
- Odor: Odorless.
- Melting Point: ~100°C (dehydration); anhydrous form melts at ~698 °C.
- Solubility in Water: Approximately 74 g/100 mL at 20°C. freely soluble pH (5% aqueous solution): Approximately 9.0 – 10.5 (alkaline)
- Stability: Stable under normal storage conditions; hygroscopic — absorbs moisture from air
Properties of Sodium Tungstate Anhydrous
- CAS Number: 13472-45-2
- Molecular Formula: Na₂WO₄
- Molecular Weight: 293.82 g/mol
- Density: 4.18 g/cm³
- Melting Point: 698°C
- Appearance: White crystalline powder
The higher density of the anhydrous form (4.18 g/cm³ vs 3.25 g/cm³ for the dihydrate) reflects the absence of the two lighter water molecules in the crystal structure.
How is Sodium Tungstate Manufactured?
Sodium Tungstate is manufactured through several established industrial routes, depending on the tungsten feedstock available.
From Tungsten Trioxide, the most common manufacturing route involves reacting tungsten trioxide (WO₃) with sodium hydroxide (NaOH) solution under controlled temperature and pressure conditions. The reaction produces a sodium tungstate solution, which is then filtered, concentrated, and crystallized to yield Sodium Tungstate Dihydrate.
From tungsten trioxide reaction:
WO₃ + 2NaOH → Na₂WO₄ + H₂O
From Scheelite or Wolframite Tungsten ore concentrates, primarily scheelite (CaWO₄) or wolframite ((Fe, Mn)WO₄), can be treated with sodium hydroxide or sodium carbonate solutions to produce sodium tungstate directly from the ore. This route is used in integrated tungsten processing facilities.
From the scheelite ore reaction:
CaWO₄ + Na₂CO₃ → Na₂WO₄ + CaCO₃
Crystallization and Drying The Sodium Tungstate Dihydrate product is obtained by controlled crystallization from the purified sodium tungstate solution. If the anhydrous form is required, the dihydrate is further dried at temperatures above 100°C to drive off the water of crystallization.
Applications of Sodium Tungstate
Flame Retardants: Tungstate compounds, including Sodium Tungstate, are used as flame retardants and smoke suppressants in polymers, textiles, and cellulosic materials. They work by promoting char formation and inhibiting combustion at the polymer surface, reducing both flame spread and toxic smoke generation.
Catalyst Production: Sodium Tungstate is used as a precursor in the manufacture of tungsten-based catalysts. Tungsten catalysts are important in petroleum refining (hydrodesulfurisation), chemical synthesis, and oxidation reactions. It is also used directly as a catalyst in certain organic synthesis reactions, particularly in selective oxidation processes using hydrogen peroxide as the oxidant.
Textile Industry: In textile processing, Sodium Tungstate is used as a mordant, a substance that fixes dyes to fabric, and as a weighting agent for silk. It improves the uptake and fastness of certain dye classes and increases the apparent weight and body of silk fabrics, a traditional application that dates back to the early twentieth century.
Pigments and Coatings: Sodium Tungstate serves as a precursor in the production of tungsten-based pigments, including tungsten bronze pigments used in specialty coatings and inks. These pigments offer unique optical properties, including near-infrared absorption and electrochromic behaviour.
Water Treatment: In water treatment applications, Sodium Tungstate is used as a corrosion inhibitor in industrial cooling water and boiler water systems, protecting metal infrastructure from oxidative degradation in continuous water circulation systems.
Sodium Tungstate vs Sodium Tungstate Dihydrate - Which Should You Source?
Choose Sodium Tungstate Dihydrate when:
- Working with aqueous formulations or solution-based processes. The dihydrate dissolves readily and is the standard commercial form for most applications.
- Handling and storage at ambient conditions. The dihydrate is more stable than the anhydrous form under normal temperature and humidity
- Preparing electroplating baths, corrosion inhibitor solutions, or laboratory reagent solutions
- Cost efficiency is a consideration - The dihydrate is the more widely available and typically more competitively priced commercial form
Choose Anhydrous Sodium Tungstate when:
- The application requires precise tungsten content on an anhydrous basis - The higher active tungsten content per gram of anhydrous material is advantageous
- High-temperature processing is involved, where residual moisture would be problematic
- Specific downstream catalyst or material synthesis processes specify the anhydrous form
For the vast majority of industrial and laboratory applications, Sodium Tungstate Dihydrate (Na₂WO₄·2H₂O, CAS 10213-10-2) is the appropriate and standard choice.
Grades and Specifications
Sodium Tungstate is commercially available in two primary forms. Sodium Tungstate Dihydrate (CAS 10213-10-2) and Sodium Tungstate Anhydrous (CAS 13472-45-2). Each supplied across multiple purity grades depending on the intended application.
Technical Grade With a purity of 98.0–98.5%, technical grade Sodium Tungstate is the standard industrial grade used in electroplating baths, corrosion inhibitor formulations, textile processing auxiliaries, and water treatment applications. It meets general industrial requirements but is not suitable for analytical, pharmaceutical, or high-precision catalyst applications.
Pure / Commercial Pure Grade With purity in the range of 98.5–99.0%, this grade is used in applications requiring tighter quality control than technical grade — including industrial catalyst support preparation, pigment production, and specialized chemical synthesis. It is the most widely traded grade in B2B supply.
Reagent Grade (ACS) Reagent grade Sodium Tungstate meets the specifications of the American Chemical Society (ACS) with purity of ≥99.0%. It is used in analytical chemistry, laboratory research, biochemical assays, and the preparation of tungsten-based reagents such as the Folin-Wu reagent used in blood glucose analysis.
High Purity Grade With purity of ≥99.5%, high purity Sodium Tungstate is used in advanced catalyst preparation, biomedical research, and specialty chemical synthesis where trace metal impurities must be minimized. Key impurities monitored include chloride (Cl), sulphate (SO₄), iron (Fe), and heavy metals.
Pharmaceutical / BP / EP Grade Where Sodium Tungstate is used in pharmaceutical or regulated biomedical applications, it must comply with relevant pharmacopoeia standards such as the British Pharmacopoeia (BP) or European Pharmacopoeia (EP). This grade requires full documentation including COA, impurity profile, and batch traceability.
Key Impurities Monitored Across all grades, the following impurities are tracked in COA documentation: chloride (Cl), sulphate (SO₄), iron (Fe), heavy metals, pH of aqueous solution, and water-insoluble matter. For reagent and high purity grades, limits are tightly controlled to single-digit ppm levels.
Frequently Asked Questions
What is Sodium Tungstate used for?
Sodium Tungstate is used in electroplating, corrosion inhibition, flame retardants, textile processing, catalyst production, water treatment, and laboratory applications such as protein precipitation and analytical chemistry.
What is the difference between Sodium Tungstate and Sodium Tungstate Dihydrate?
Sodium Tungstate Dihydrate (Na₂WO₄·2H₂O) contains two molecules of water of crystallisation incorporated into its crystal structure. The anhydrous form (Na₂WO₄) does not. The dihydrate is the standard commercial form for most applications and is more stable under ambient storage conditions. The anhydrous form has a higher tungsten content per gram and a significantly higher density.
What is the shelf life of Sodium Tungstate?
The shelf life of sodium tungstate is 2–3 years from the date of manufacture when stored in tightly sealed containers in a cool, dry place. Being hygroscopic, containers must be kept closed at all times to prevent moisture absorption and caking.
What is another name for Sodium Tungstate?
Sodium Tungstate is also known as Disodium Tungstate, Sodium Orthotungstate, and Sodium Wolframate. The dihydrate form is commonly referred to as Sodium Tungstate Dihydrate.
What is the purity of Sodium Tungstate?
Technical grade offers a minimum purity of 98%, suitable for most industrial applications. Reagent or ACS grade offers 99% minimum purity for laboratory use. Always request a batch-specific COA from your supplier confirming actual purity.
Is Sodium Tungstate toxic?
Sodium Tungstate has relatively low acute toxicity and is not classified as a carcinogen. Standard precautions apply. Avoid dust inhalation, prolonged skin contact, and eye exposure. Always refer to the supplier's Safety Data Sheet (SDS) for full handling guidance.
Looking for a reliable Sodium Tungstate supplier? Scimplify offers high-purity Sodium Tungstate and Sodium Tungstate Dihydrate in bulk quantities with complete documentation, batch-specific COA, and reliable. Get in touch with our team today to request a quote or sample.
Email us to info@scimplify.com