| HS Code | 404248 |
| Chemical Formula | Na2SeO3 |
| Cas Number | 10102-18-8 |
| Grade | Industrial Grade |
| Appearance | White crystalline powder |
| Purity | 98% min |
| Selenium Content | 45.7% typical |
| Solubility | Soluble in water; slightly soluble in ethanol |
| Melting Point | 710°C (decomposes) |
| Density | 3.1 g/cm3 |
| Toxicity | Highly toxic; acute oral LD50 (rat) ~7 mg/kg |
| Hygroscopicity | Slightly hygroscopic; keep sealed and protected from moisture |
| Storage Conditions | Store in cool, dry, well-ventilated area; keep container tightly closed |
As an accredited Industrial Grade Sodium Selenite factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 25 kg fiber drum with double PE liner, sealed and labeled with hazard warnings for industrial-grade sodium selenite. |
| Container Loading (20′ FCL) | Industrial Grade Sodium Selenite loaded in 20′ FCL, drum-packed, secured, labeled hazardous, sealed for safe transport. |
| Shipping | Industrial Grade Sodium Selenite is shipped as a toxic hazardous material (UN 2630, Class 6.1). It requires sealed, corrosion-resistant packaging, clear toxic labels, and full transport documentation. Shipments must comply with international regulations (IMDG, IATA, ADR), with proper segregation from foodstuffs and emergency spill procedures in place. |
| Storage | Store in a cool, dry, well-ventilated area away from direct sunlight, heat sources, and incompatible materials such as strong acids and reducing agents. Keep the container tightly sealed to prevent moisture absorption and contamination. Segregate from foodstuffs and animal feed. Use appropriate labeling and secondary containment. Ensure access is restricted to authorized personnel. |
| Shelf Life | Shelf life is typically 2 years from manufacture date when stored unopened in a cool, dry, well-ventilated area. |
Animal feed premix production using industrial-grade sodium selenite is a micro-ingredient operation in which the control variable is elemental selenium rather than the bulk weight of the salt. Anhydrous Na2SeO3 with a minimum assay of 98.0 wt% carries approximately 45.7% elemental selenium, while the pentahydrate carries approximately 30.0%; failure to normalize the charge against the certificate of analysis therefore creates batch-to-batch variance before any production loss occurs. The regulatory boundary in the United States under 21 CFR 573.920 limits supplemental selenium from sodium selenite in complete poultry and swine diets to 0.3 mg/kg complete feed. In the European Union, formulation is governed by Regulation (EC) No 1831/2003 for feed additive status and Directive 2002/32/EC for maximum total selenium in complete feedingstuffs; the applicable numerical limit is species-specific and shall be confirmed against the current Annex. Direct addition of pure sodium selenite is stoichiometrically possible at 0.657 g anhydrous Na2SeO3 per tonne to deliver 0.3 mg Se/kg, derived from the selenium fraction, but direct metering is rejected on production lines because micro-ingredient scales with a precision of ±0.1% cannot guarantee uniform distribution at that mass without creating toxic hot spots. The operational solution is carrier dilution: a 1.0% Se premix is made by blending 2.19 kg anhydrous Na2SeO3 into 97.81 kg calcium carbonate or wheat middling carrier per 100 kg premix, while a 0.5% Se premix uses 1.09 kg Na2SeO3 and 98.91 kg carrier. The diluted premix is then dosed at 30 g or 60 g per tonne complete feed respectively to supply 0.3 mg Se/kg. This dilution shifts the metered mass into the range of a production-scale loss-in-weight screw feeder and allows the mixer to achieve a tracer-validated coefficient of variation below 10% for selenium.
| Premix target | Anhydrous Na2SeO3 per 100 kg premix | Premix dosage per tonne complete feed | Elemental Se supplied |
| 1.0% Se | 2.19 kg | 30 g | 0.3 mg/kg |
| 0.5% Se | 1.09 kg | 60 g | 0.3 mg/kg |
Premix manufacturing is typically executed in a horizontal paddle mixer with staged addition of one-half carrier, sodium selenite, the remaining carrier, and a dust suppressant; mixing time is not fixed by simple residence time but is validated by tracer recovery at the critical control point. Because sodium selenite is water-soluble and hygroscopic above moderate relative humidity, storage before mixing requires sealed containers and a dry pack-out environment, particularly at relative humidity above 60%. Dust collection and negative pressure transfer are mandatory because selenium-containing dust escaping the mixer changes worker exposure and housekeeping classification. Terminal finished products leaving this downstream segment include pelleted broiler and layer feeds, swine grower-finisher rations, and loose mineral premixes for on-farm mixing.
Industrial-grade sodium selenite enters glassmaking as a source of elemental selenium after thermal decomposition in the batch melt, and the transition from decolorizing to pink or ruby tint is governed by redox potential rather than by raw salt weight alone. In the furnace, sodium selenite decomposes initially to SeO2 and then to elemental selenium under mildly reducing conditions; excessive reduction can form selenide species and shift the color response, while overly oxidizing conditions raise volatilization losses of selenium dioxide. Reported selenium volatilization losses may reach 40% before fining, which is why batch calculations must compensate for furnace atmosphere and cullet ratio rather than assuming full retention. Batch addition is determined by the target Se equivalent in the glass: typical decolorizing additions for clear container and flat glass are 0.01–0.15 kg Se/t glass, while pink and selenium ruby formulations may require 0.1–0.5 kg Se/t, corresponding to 0.022–0.33 kg and 0.22–1.10 kg anhydrous Na2SeO3 per tonne respectively, assuming 45.7% Se. These values are starting points, because fining conditions, iron content, cullet oxidation state, and furnace type shift retained selenium; published data for a specific furnace configuration is limited and shall be generated from production-scale furnace trials.
The production sequence includes dispersion through a premixed glass batch containing silica sand, soda ash, limestone, and broken cullet at 20–40% cullet. The batch is mixed in a low-shear batch mixer, transferred to a regenerative end-fired or oxy-fuel furnace, and melted at 1480–1530°C. Redox control is maintained through controlled carbon addition, salt cake ratio, or burner atmosphere adjustment; insufficient reduction increases selenium losses, while excessive reduction pulls iron into the Fe2+ blue-green state and can muddy the intended pink compensation. Selenium-containing condensates in regenerator checkers, batch filters, and dust extraction residues must be handled as hazardous residues. Flat and architectural glass is specified under ASTM C1036-21 and EN 572-2:2012, with optical and thermal properties measured under ISO 9050:2003. Food-contact glass containers fall under Regulation (EC) No 1935/2004, and selenium release from finished glass is controlled through applicable national provisions for glass packaging. Terminal finished products include flint container glass, architectural glazing with reduced green cast, pink tableware, and tinted packaging glass.
Where a selenium donor more readily dispersible than elemental selenium is required, cadmium sulfoselenide pigment manufacturing consumes industrial-grade sodium selenite through a wet precipitation or solid-state calcination route. The product composition is defined by the Se/(S+Se) mole fraction; red and orange pigments commonly occupy 0.10–0.35 Se mole fraction. A 0.25 Se fraction requires 0.25 mol Na2SeO3 per mole of cadmium in the final sulfide-selenide solid solution, equivalent to 43.2 g anhydrous sodium selenite per mole of pigment cadmium. Compliance is two-fold: the cadmium carrier is subject to REACH Annex XVII Entry 23 restrictions in certain plastic and coating articles, and the pigment shall be tested for selenium migration under EN 71-3:2019+A1:2021 if intended for toy or childcare applications. The production sequence includes dissolution of sodium selenite, controlled precipitation of a mixed cadmium sulfide-selenide intermediate, washing, calcination in an inert atmosphere at 400–600°C, and wet milling to a final particle size below 1.0 μm average diameter. During calcination, selenium loss can occur if oxygen enters the rotary calciner or if the temperature overshoots the solid-state reaction window; sealed discharge and nitrogen purge are therefore specified. Terminal finished products include cadmium sulfoselenide red and orange pigments for ceramic stains, engineering plastics where cadmium is permitted, and artist-grade pigments subject to heavy metal labeling.
In ceramic enamel and frit production, sodium selenite is milled into the frit batch to supply selenium red during low-temperature firing, where the selenium must remain chemically available until the glassy phase seals. Typical Se additions are 0.05–0.4 wt% of frit batch, corresponding to 0.11–0.88 wt% anhydrous Na2SeO3; higher additions are generally limited by volatilization losses and blistering. Compliance for tableware and decorative tile applications includes EN 71-3:2019+A1:2021 for selenium migration where the article is used by children and Regulation (EC) No 1935/2004 for food-contact ceramic goods. The production sequence includes dry blending or wet milling sodium selenite into a ceramic slip or screen-printing vehicle, application by dipping, spraying, or direct printing, and firing at 650–850°C; the firing curve shall include a dwell below the glaze sealing point to allow decomposition products to escape without pinholing. Terminal finished products include selenium red dinnerware, enameled signage, ceramic tiles, and decorative glass enamels.
Sodium selenite is used in selenium-poor agricultural regions as an inorganic selenium carrier for soil and foliar application, but the application boundary is narrow because selenite adsorbs to iron and aluminum oxyhydroxides and shows lower phloem mobility than selenate. National programs in selenium-deficient soils have documented field application rates of 5–10 g Se/ha per season, with granular NPK formulations carrying 15–20 mg Se/kg; sodium selenite pentahydrate at 30.0% Se requires 50–67 g pentahydrate per tonne of fertilizer to achieve that concentration before soil adsorption is considered. Regulatory placement in the European Union is governed by Regulation (EU) 2019/1009 where the fertilizing product falls within its scope, and by national provisions where selenium is authorized as a beneficial element; formulators shall not assume automatic EU-wide acceptance for a selenium-containing fertilizer under the FPR. The manufacturing process for granular product is a two-stage operation: sodium selenite is first dissolved in water in an acid-resistant tank, then sprayed onto a moving bed of NPK granules or inert carrier at or below 70°C, followed by forced-air drying to preserve granule crush strength. Foliar products are prepared as low-concentration solutions and applied with spray drift controls to avoid selenium exposure. Terminal finished products include selenium-enriched cereal grains, forage legumes, and canola processed for feed and food use; crop uptake from selenite differs by soil pH and organic matter, and published data for non-calcareous soils is limited, requiring local field calibration.
Conversion of industrial-grade sodium selenite to selenium dioxide is a downstream chemical unit operation rather than a formulation; the mass balance is fixed by the acid choice and the hydration state of the salt. Anhydrous Na2SeO3 reacts with sulfuric acid according to the stoichiometry Na2SeO3 + H2SO4 → SeO2 + Na2SO4 + H2O, so 172.9 g of anhydrous sodium selenite yields 111.0 g SeO2 after complete dehydration, a mass efficiency of 64.2%. The reaction is carried out in a glass-lined or enameled reactor at 40–60°C under pH control below 2; selenium dioxide is recovered by vacuum crystallization, filtered, and dried at 105°C. Compliance obligations arise from the hazard classification of sodium selenite and selenium dioxide under CLP, with sealed transfer and scrubber capture of selenium vapors; REACH registration and downstream user exposure scenarios shall be updated for the receiving electrolyte formulator. The terminal products from this segment include selenium dioxide reagent for controlled oxidation syntheses, selenite-containing electrolyte concentrates for electrodeposition of selenium films, and chemical baths for metal coloring where the specific bath formulation is validated by bath analysis. Published data for proprietary electrodeposition recipes employing sodium selenite-derived selenium dioxide is limited; a formulator shall perform Hull cell and titration trials before scaling to production.
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Industrial Grade Sodium Selenite is supplied as a white to off-white crystalline powder with the chemical formula Na2SeO3 and a molecular weight of 172.94 g/mol. The product identified by CAS registry number 10102-18-8 and EINECS number 233-267-9 is the anhydrous sodium salt of selenious acid; industrial material is normally not the pentahydrate, and the anhydrous form is preferred for high-temperature applications because hydrate dehydration consumes energy and can alter melting behaviour in glass batches. A representative industrial specification is built around a minimum assay of 98.0% Na2SeO3 on a dry basis, equivalent to a theoretical selenium content of 45.67% and a commercial guarantee of not less than 44.5% selenium. The powder has a bulk density typically in the range 1.1–1.4 g/cm3 and an aqueous solubility of approximately 85 g/100 mL at 20°C for the anhydrous material. Packaging is commonly 25 kg or 50 kg fibre drums with polyethylene liners, or 500 kg flexible intermediate bulk containers. Industrial grade differs from reagent and feed grades by the permitted level of non-selenium metal impurities, sulfate, chloride, and insoluble matter, and by the absence of regulatory certificates for direct feed or pharmaceutical use.
Representative physical and chemical specifications are listed in Table 1. The limit values are composite industrial data and must be confirmed against the supplier’s certificate of analysis before use. Commercial model designations are supplier-specific; a representative code Na2SeO3-IG98 denotes industrial grade with minimum 98% assay, while trailing digits often indicate a nominal screen cut.
| Parameter | Representative limit | Test method or reference |
|---|---|---|
| Appearance | White to off-white crystalline powder | Visual inspection |
| Purity as Na2SeO3, dry basis | ≥ 98.0% | Iodometric titration after acid dissolution |
| Selenium content | ≥ 44.5% | ICP-OES per ISO 11885:2007 or gravimetric reduction |
| Loss on drying | ≤ 0.5% | 105°C to constant mass, ISO 787-2:1981 |
| Water-insoluble matter | ≤ 0.05% | ISO 787-3:2000 |
| Chloride as Cl | ≤ 0.05% | Turbidimetric comparison |
| Sulfate as SO4 | ≤ 0.1% | Turbidimetric barium sulfate |
| Arsenic | ≤ 10 mg/kg | ICP-OES per ISO 11885:2007 |
| Cadmium | ≤ 5 mg/kg | ICP-OES per ISO 11885:2007 |
| Lead | ≤ 20 mg/kg | ICP-OES per ISO 11885:2007 |
| pH, 1% solution | 7.0–9.0 | Potentiometric, ASTM E70 |
Table 2 compares the industrial material with reagent and feed grades. The boundaries are regulatory and analytical rather than strictly compositional; some industrial lots may approach the purity of feed grade, but documentation and compendial status are not equivalent.
| Attribute | Industrial grade | Reagent grade | Feed grade |
|---|---|---|---|
| Purity as Na2SeO3, dry basis | ≥ 98.0% | ≥ 98.0–99.0% | ≥ 98.0% |
| Selenium content | ≥ 44.5% | ≥ 45.0% | ≥ 44.5% |
| Lead | ≤ 20 mg/kg | ≤ 5 mg/kg | Compendial limit |
| Arsenic | ≤ 10 mg/kg | ≤ 5 mg/kg | Compendial limit |
| Cadmium | ≤ 5 mg/kg | ≤ 5 mg/kg | Compendial limit |
| Regulatory documentation | Certificate of analysis, REACH SDS | Certificate of analysis with ACS/ISO monograph testing | Feed additive authorisation under 21 CFR 573.920 or Regulation (EC) No 1831/2003 |
| Typical use | Glass, pigment, selenium metal precipitation, metal finishing | Laboratory synthesis, reagent preparation, analytical standards | Premix and complete feed selenium fortification |
Industrial grade sodium selenite is not interchangeable with feed or USP-grade material without additional purification and release testing. In the European Union, selenium compounds intended for animal nutrition are regulated under Regulation (EC) No 1831/2003, and total selenium in complete feed is subject to a maximum of 0.5 mg/kg with species-specific restrictions. In the United States, 21 CFR 573.920 establishes the conditions for selenium supplementation of animal feed and limits added selenium in complete feed to 0.3 mg/kg. Industrial grade material is typically manufactured for reduction, glass, and pigment operations where impurity sensitivity is driven by furnace redox or precipitation selectivity, not by monogastric toxicity or tissue residue. For example, arsenic and cadmium in industrial sodium selenite may be tolerated at ≤ 10 mg/kg and ≤ 5 mg/kg respectively, while feed monographs routinely require lower limits and additional identity, loss on drying, and selenite/selenate speciation documentation. Because industrial material is not supplied with a feed-additive dossier or a certificate of suitability, its direct use in premix production is outside the scope of the regulatory authorisation unless the manufacturer re-qualifies the lot against the applicable compendial or feed monograph. The same separation applies to pharmaceutical intermediates, where current good manufacturing practice and change control documentation are mandatory; industrial grade may serve as a starting material for the synthesis of downstream selenium compounds, but only after controlled purification and analytical release testing.
Glass decolorising and colour generation represents a major industrial outlet for sodium selenite. In soda-lime-silica container and flat glass, the compound is introduced in the batch or as a premixed minor addition to offset the green tint produced by iron. The active species is reduced in the melt from Se(IV) to Se(0) and to selenide species, the valence state distribution being controlled by furnace atmosphere, batch redox agents, and cullet ratio. Selenium dioxide formed during heating has a sublimation point near 315°C; once the batch passes through the solid-state heating zone, volatile selenium oxides can escape before incorporation into the silicate network. Because selenium retention in the melt is strongly influenced by furnace temperature and redox balance, the relation between added sodium selenite and residual selenium in the glass is not linear. On a cross-fired regenerative furnace melting approximately 300 t/day of flint container glass, process conditions are commonly adjusted to achieve residual selenium in the glass of a few tens of milligrams per kilogram; exact addition rates must be determined by furnace-specific trials because published retention data for this configuration is limited. Too high an addition relative to the available reducing agents generates grey selenium particles and can produce amber or grey glass, while too low an addition leaves a yellow-green cast. The product is normally weighed with a minor-ingredient dosing system capable of ±1% dosing accuracy to avoid colour drift. Baghouse dust from the furnace may contain selenium and must be routed to a permitted selenium recovery or waste-treatment stream.
Industrial grade sodium selenite is converted to elemental selenium in precipitation circuits used for metallurgical and chemical manufacture. The selenite is dissolved in demineralised water to form a clear solution, acidified to pH 2.0–3.0 with sulfuric or hydrochloric acid, and treated with a reducing agent. Sulfur dioxide, sodium sulfite, hydrazine hydrate, and ascorbic acid are all technically competent; sulfur dioxide is preferred for high-volume production because the resulting by-product is sulfuric acid, which is removed with the mother liquor. The overall reduction of acidified selenite to selenium with sulfur dioxide proceeds according to the reaction H2SeO3 + 2 SO2 + H2O → Se + 2 H2SO4. The initially precipitated selenium is the red amorphous allotrope. Further digestion at 85–95°C for 30–60 min converts the red allotrope to the denser grey selenium, which is easier to filter. The endpoint is monitored by measuring the residual selenite concentration in the supernatant using an iodometric method or ICP-OES per ISO 11885:2007. Particle size after grey conversion is governed by the stirring regime: on a 2000 L glass-lined reactor equipped with a pitched-blade turbine, tip speeds between 1.5 m/s and 3.0 m/s are maintained to prevent agglomeration without incorporating excessive air. The slurry is discharged through a nutsche filter, washed with warm demineralised water at 60°C, and dried under nitrogen at 80–100°C. The final powder is screened to a controlled particle-size distribution, commonly 75–150 µm. The use of sodium selenite rather than selenious acid reduces the initial acid inventory and the corrosion load on the reactor. However, sodium selenite dissolution is endothermic and may require steam-heated jacketing in cold climates to maintain a feed temperature above 20°C.
Processes that require selenium(IV) in a less aggressive pH window use industrial grade sodium selenite instead of selenious acid or selenium dioxide. In cadmium sulfoselenide pigment production, the sodium salt is dry-mixed with cadmium sulfide and sulfur-bearing compounds and calcined in a rotary kiln at 550–650°C. The sodium ion acts as a fluxing agent and reduces the calcination temperature required for phase formation. Colour control is exercised by the Se/(Se+S) molar ratio, with higher selenium fractions producing deeper red hues. Because sodium selenite is non-hygroscopic and free-flowing, weight-in accuracy in automatic pigment batching is more stable than with selenium dioxide, which can be hygroscopic and sticky in humid conditions. The shift from sulfur to selenium is not linear; small changes in the Se/(Se+S) ratio at the orange-to-red transition can produce more visible colour change than similar changes in the yellow-to-orange region, so the selenium source must be specified for sampling homogeneity and particle size. In alkaline copper-blackening baths, sodium selenite is used as the source of selenite ions that deposit a black copper-selenide conversion layer on brass and copper. A typical bath contains sodium selenite at 10–30 g/L and is operated at 60–80°C with continuous filtration. The work-piece surface must be oxide-free before immersion; otherwise the conversion layer forms unevenly. Spent baths and rinse waters are treated with iron salts or zero-valent iron to precipitate selenium below discharge limits, because Se(IV) is toxic to aquatic organisms. Industrial grade material may be used for these engineering applications because the metallic impurities do not interfere with colour development or adhesion.
Handling and waste-treatment constraints complete the technical profile of industrial grade sodium selenite. The powder is toxic if swallowed and hazardous to aquatic life; the US OSHA permissible exposure limit for selenium compounds is 0.2 mg/m3 as selenium, measured as an 8-hour time-weighted average. Ventilation or respiratory protection is required when bag dumping into a hopper because fine dust below 10 µm can remain airborne. Acid contact liberates selenious acid and, with strong reducers, can generate elemental selenium sludge; storage segregation from acids and reducing agents is therefore required. Facilities using sodium selenite in glass, pigment, or metal precipitation must treat scrubber water and floor washings to meet local selenium discharge limits, which in some jurisdictions are below 0.02 mg/L. The product falls under REACH registration obligations in the European Union under Regulation (EC) No 1907/2006; downstream users are expected to apply the exposure scenarios communicated in the extended safety data sheet for their process categories. No direct food or feed use is permitted for industrial grade material without downstream re-qualification against the applicable food or feed monograph.