| HS Code | 510478 |
| Chemical Formula | Na2SeO3 |
| Molecular Weight | 172.94 g/mol |
| Cas Number | 10102-18-8 |
| Appearance | White crystalline powder |
| Purity | ≥98% (high purity grade) |
| Solubility | Soluble in water; slightly soluble in ethanol |
| Melting Point | >350 °C (decomposes) |
| Density | 3.1 g/cm3 |
| Storage Conditions | Store in tightly closed container in cool, dry, well-ventilated area |
| Hazard Classification | Toxic if swallowed; dangerous for the environment |
| Selenium Oxidation State | +4 |
| Physical Form | Fine crystalline powder |
As an accredited Sodium Selenite High Purity factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Sodium Selenite High Purity is packaged in 25 kg fiber drums with inner polyethylene liner, ensuring stability and contamination-free storage. |
| Container Loading (20′ FCL) | 20′ FCL container loading for high-purity Sodium Selenite: secure, sealed drums/pails, proper labeling, ventilation, and spill containment ensure safe transport. |
| Shipping | Sodium Selenite High Purity ships in sealed, corrosion-resistant containers, clearly labeled as toxic. Ground transport only, away from incompatible materials. Ensure compliance with hazardous goods regulations, proper ventilation, and secondary containment to prevent spillage. Handle with care; avoid exposure to moisture and direct sunlight. |
| Storage | Store Sodium Selenite High Purity in a tightly sealed container in a cool, dry, well-ventilated area, away from direct sunlight and moisture. Keep separate from acids, reducing agents, and foodstuffs. Ensure proper labeling and secure storage to prevent accidental exposure, as it is toxic. |
| Shelf Life | Store tightly sealed in a cool, dry area. Shelf life is typically 2-3 years from manufacture date. |
Accurate delivery of 0.3 mg/kg total selenium in monogastric and ruminant complete feed, as permitted under 21 CFR 573.920, requires a stoichiometric correction based on the 45.65% selenium content of anhydrous Na2SeO3 (molecular weight 172.94 g/mol). The equivalent Na2SeO3 mass in finished feed is 0.657 g/tonne for the United States limit and 1.095 g/tonne for the European Union maximum of 0.5 mg/kg under Regulation (EC) No 1831/2003. In a 0.5% inclusion mineral premix, this translates to 131–219 mg/kg Na2SeO3, depending on the regional limit and target species. For high-purity feed-grade material, supplier certificates of analysis should include assay and trace-metal results generated under ISO/IEC 17025:2017 to limit arsenic, cadmium, lead, and mercury carryover into the premix.
| Regulatory Domain | Standard Designation | Complete Feed Se Limit | Equivalent Na2SeO3 |
|---|---|---|---|
| United States | 21 CFR 573.920 | 0.3 mg/kg | 0.657 g/tonne |
| European Union | Regulation (EC) No 1831/2003 | 0.5 mg/kg | 1.095 g/tonne |
Commercial premix batching does not add Na2SeO3 directly to finished feed. The compound is first extended by geometric dilution into a 1.0–2.0% selenium trituration using calcium carbonate or wheat middlings as carrier; the carrier is pre-conditioned to <12% moisture and <35 °C to prevent caking during storage. A 2,000 kg double-ribbon mixer operating at 30–50 rpm for 10–15 minutes typically yields a microingredient coefficient of variation <5% when sampled at 10 points and assayed by ICP-MS following microwave-assisted acid digestion per EN 17053:2018. Pelleting lines use steam conditioning at 70–85 °C for 20–40 seconds; selenium recovery is checked at the die outlet because localized steam condensation can mobilize water-soluble Se(IV) into recycled fines, creating batch-to-batch variance if the fines stream is re-added without assay.
Operational boundaries include avoidance of direct liquid feed incorporation with ascorbic acid or reducing sugars at pH <4.0, because Se(IV) can reduce to red elemental selenium precipitate and settle in distribution lines. For dry premixes containing ascorbic acid, separate addition lines or hydrophobic-barrier-coated Na2SeO3 granules are required when equilibrium relative humidity exceeds 60%. Finished feed articles produced from this application include pelleted and crumbled complete feed for poultry, swine, and ruminants; loose mineral premixes; molasses-based lick blocks; and free-choice trace-mineral tubs.
In the batch house, Na2SeO3 is weighed with sand, soda ash, limestone, and cullet. During the batch-to-melt transition, the compound decomposes and releases SeO2, which dissolves into the alkaline silicate melt and participates in the Fe2+/Fe3+ redox equilibrium. The colour correction effect is therefore not a simple pigment addition; it depends on the simultaneous control of batch redox number, sulfate-to-carbon ratio, and iron content. Published batch data for flint decolourising typically express selenium additions as 0.0005–0.02 wt% Se, equivalent to 0.0011–0.044 wt% Na2SeO3, while selenium ruby glass may use higher selenium additions up to 0.05–0.2 wt%; exact addition levels are furnace-specific and depend on Fe2O3 content, cullet ratio, and desired colour coordinates. Published data for a specific production furnace is often limited because redox conditions and exhaust draft differ materially between oxy-fuel and regenerative units.
Melting is performed in continuous regenerative or oxy-fuel furnaces at 1450–1550 °C, with batch residence times of 24–48 hours and cullet ratios of 30–60%. Sodium selenite additions are made through the batch charger, and the resulting melt is refined with sulfate plus carbon to maintain the required redox number before forehearth conditioning at 1100–1200 °C. Furnace exhaust volatilisation is a recognized processing bottleneck because selenium may enrich baghouse dust; this dust requires controlled recycling or disposal according to REACH (EC) 1907/2006 and local emission permits. Chemical analysis of finished glass for selenium and iron is conducted per ASTM C169-16, and finished colour coordinates are evaluated using CIE L*a*b* spectrophotometry per ISO 11664-4:2008.
Amber glass production is an unsuitable application because the amber chromophore depends on polysulfide/Fe3+ conditions under a reduced melt state; the oxidising character of selenite can shift the melt away from the amber absorption profile. The glass articles produced under this controlled redox condition include flint container glass, pressed and blown tableware, and colour-corrected packaging glass where improved luminous transmittance is specified.
Potentiostatic deposition of CuInSe2 absorber layers from sulfate–citrate baths uses Na2SeO3 as the dissolved Se(IV) precursor at pH 1.8–2.2. Typical working baths contain 2–5 mmol/L Na2SeO3, 2–3 mmol/L CuSO4·5H2O, 2–4 mmol/L In2(SO4)3, and 0.1–0.5 mol/L trisodium citrate as complexing agent; citrate concentration is set to prevent indium hydroxide precipitation above pH 2.5. Deposition is conducted in a three-electrode cell with a molybdenum-coated soda-lime glass cathode, platinum anode, and Ag/AgCl reference, using potentiostatic or pulsed deposition at -1.0 to -1.4 V vs Ag/AgCl. Bath temperature is held at 25±1 °C with controlled stirring to maintain a uniform diffusion layer; deposition time is 30–90 minutes for 1.5–2.5 µm thick films. Bath ageing is severe because Se(IV) can reduce to colloidal red Se(0) in the presence of dissolved Cu+ or reducing impurities; continuous 0.2 µm cartridge filtration and low dissolved oxygen are required to control particulate defects. pH below 1.5 induces hydrogen evolution and porous deposits, while pH above 2.5 precipitates indium hydroxide on the substrate and creates non-uniform composition.
After deposition, the precursor film is annealed in a selenium-containing atmosphere at 550–600 °C for 10–30 minutes to improve crystallinity and adjust the Cu/In/Se stoichiometry; rapid thermal processing equipment with quartz-chamber heating rates of 2–5 °C/s is commonly used. Film composition is verified by ICP-OES per ASTM E1479-16; finished mini-modules are tested according to IEC 61215-1:2021 for design qualification and type approval. Downstream photovoltaic products generated from this processing route include CIGS thin-film photovoltaic modules, building-integrated photovoltaic glass laminates, and flexible metal-foil photovoltaic sheets. The electrolyte is not compatible with high chloride-containing salts because chloride-induced pitting of the molybdenum back contact can occur. Published data for full-scale industrial CIGS lines is often proprietary, but the parameter window above is consistent with peer-reviewed electrodeposition literature for Na2SeO3-based baths.
At 20–35 °C, immersion systems produce uniform black selenide-based conversion coatings on copper-rich substrates when sodium selenite is combined with copper sulfate at pH 1.5–2.0. Working concentrations are typically 5–20 g/L Na2SeO3 and 10–30 g/L CuSO4·5H2O, with pH adjusted by dilute H2SO4. The coating forms by replacement and precipitation reactions that deposit mixed copper selenide phases with thickness of 1–3 µm. The process sequence includes alkaline degreasing, acid activation, immersion for 3–10 minutes, counterflow rinsing, and drying below 80 °C before optional wax or oil topcoat application. Polypropylene immersion tanks with lateral overflow and continuous 20 µm filtration reduce suspended particle deposition; drag-out is controlled by drip trays and double counterflow rinse stations.
Corrosion performance of coated components is evaluated by neutral salt spray per ISO 9227:2022 with acceptance criteria set by the end user; adhesion is assessed by cross-cut test according to ISO 2409:2013. Parts exiting this conversion line include architectural bronze hardware, lighting fixtures, decorative plaques, and firearm components. Operational boundary: bath life is limited by copper accumulation and organic drag-out; published data for this specific configuration is limited because many industrial formulations are proprietary. The bath is highly acidic and must not be mixed with cyanide-containing cleaners or ammonia-based rinses due to the risk of toxic gas evolution.
Aseptic compounding of multi-trace-element injections incorporates sodium selenite as a source of Se(IV) in concentrations of 60 µg Se/mL for single-entity presentations and proportionally lower concentrations in combination products. A typical adult parenteral nutrition dose of 60–100 µg Se/day corresponds to 131–219 µg/day Na2SeO3; compounding pharmacies weigh the active using calibrated microbalances and dissolve it in water-for-injection with pH adjustment to 2.0–3.0 to maintain stability before aseptic filtration. The solution is processed in ISO Class 5 laminar airflow under USP <797> for sterile compounding, passed through a 0.22 µm sterile filter, and filled into depyrogenated glass vials or polymer bags. Bacterial endotoxin is controlled per USP <85>; elemental impurities are assessed under ICH Q3D with selenium-specific limits segregated from toxic metal classes.
In multi-trace-element admixtures, precipitation risk increases when sodium selenite is combined with calcium, phosphate, or iron salts at neutral pH; therefore, separate trace element admixtures or acidified stock solutions are prepared. The finished product must not be mixed directly with lipid emulsions before addition to the parenteral nutrition solution because emulsion destabilization can occur. Storage is controlled at 2–8 °C for compounded preparations, with protection from light to prevent Se(IV) photoreduction. Pharmacy-dispensed presentations produced through this aseptic route include single-entity selenium injection, lyophilized multi-trace-element cakes for reconstitution, and pharmacy-compounded total parenteral nutrition admixtures.
Because the active concentration is too low for direct addition, blending of 0.11–0.44 mg Na2SeO3 per tablet or capsule—equivalent to 50–200 µg Se per serving—requires a 1% trituration. The trituration is prepared by geometric dilution with microcrystalline cellulose or dicalcium phosphate dihydrate; carrier particle size is selected in the 75–150 µm range to minimize segregation. A 500 L V-blender operating at 15–20 rpm for 15–20 minutes typically achieves acceptable blend uniformity when sampled at 10 locations and assayed by ICP-MS. Tablets are compressed at 10–25 kN compression force and 6–8 kp hardness; capsules are filled using tamping or dosator equipment with weight variation controlled per USP <905>. Disintegration is tested according to USP <2040>, and elemental impurities follow ICH Q3D.
Chewable or gummy formats containing reducing sugars are an operational boundary because Se(IV) can reduce to red elemental selenium over time, producing visible red specks. Packaging in HDPE bottles with desiccant canisters and induction-sealed liners is used when ambient moisture is above 60% RH. Published data for long-term stability of sodium selenite in multi-vitamin mineral tablets indicates that acidic coatings with ascorbic acid may accelerate selenium loss; therefore, barrier-coating or separation of selenium and ascorbic acid in layered tablets is required when both actives are present. Solid oral dose products manufactured within these constraints include selenium tablets, two-piece hard gelatin capsules, vegetarian capsules, and unit-dose oral powder sticks.
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Sodium selenite high purity is the anhydrous sodium salt of selenious acid, CAS 10102-18-8, EINECS 233-267-9, with the linear formula Na2SeO3 and a formula mass of 172.94 g mol−1. The theoretical selenium content of the anhydrous species is 45.66%, which distinguishes it from the pentahydrate form containing approximately 30.0% selenium by mass. Commercial high-purity material is typically supplied as a white to off-white free-flowing powder with a minimum assay of 99.0% on the anhydrous basis; trace-metal limits are often set at or below 100 mg/kg total, with lead, arsenic, cadmium, and mercury individually controlled to pharmacopoeial or feed-safety thresholds. Product designations such as “anhydrous reagent grade,” “high-purity glass grade,” or “feed supplement grade” are not interchangeable: each designation reflects a distinct impurity budget involving chloride, sulfate, selenate, residual moisture, water-insoluble matter, and particle-size distribution. The high-purity product is specified at ≤0.005% chloride, ≤0.01% sulfate, and ≤0.5% loss on drying. Where a particular lot is intended for high-sensitivity applications, the certificate of analysis should be reviewed for selenate content and total oxidizing residues because these parameters control downstream redox behavior. Standard packaging commonly includes 25 kg fiber drums with polyethylene liners and 1 kg or 5 kg high-purity reagent bottles; micronized free-flowing forms are used where rapid dissolution is required, but their larger specific surface area increases moisture uptake compared with crystalline material.
High-purity sodium selenite differs from sodium selenate in oxidation state, selenium mass fraction, and redox behavior. Selenite contains selenium in the +4 oxidation state, whereas selenate contains selenium in the +6 state. The anhydrous selenite has a theoretical selenium content of 45.66%, while anhydrous sodium selenate has a theoretical selenium content of approximately 41.8%. In aqueous systems, selenite is more readily reduced to elemental selenium or selenide than selenate, which requires stronger reducing conditions. This difference is exploited in controlled nanoparticle synthesis and in metal finishing baths: selenite reacts rapidly with ascorbic acid at pH 5.5–6.5 to generate colloidal selenium, whereas selenate reduction under the same conditions is kinetically limited. In glass redox chemistry, the selenite form decomposes at a lower energy input than selenate and provides a more direct route to the selenium species responsible for pink compensation of iron green. The two salts are not interchangeable in feed formulations without revalidation, because the bioavailability, regulatory status, and analytical recovery can differ even though both are permitted selenium sources under 21 CFR 573.920.
The practical distinction is not the selenium content—every anhydrous sodium selenite sample provides the same theoretical 45.66% selenium—but the level of redox-active and heavy-metal contaminants that survive crystallization. Technical grades may contain sulfate and selenate at levels sufficient to alter glass redox balance or to interfere with animal premix homogeneity. High-purity lots are washed, recrystallized, and dried under controlled conditions to reduce chloride below 0.005%, sulfate below 0.01%, and heavy metals as lead below 10 mg/kg; feed-grade material may be released against a less stringent heavy-metal budget but must still meet the source and labeling requirements of 21 CFR 573.920. For glassmaking, high-purity material is used when trace-heavy-metal carry-over into packaging glass must be minimized or when furnace redox balance is sensitive to sulfate. For animal nutrition, the high-purity input is chosen to reduce co-delivered impurities in concentrated premixes rather than to increase the permitted selenium dose.
| Parameter | High-purity reagent | Feed premix grade | Technical glass grade |
|---|---|---|---|
| Assay as Na2SeO3 | ≥ 99.0% | ≥ 98.0% | ≥ 96.0% |
| Chloride (Cl) | ≤ 0.005% | ≤ 0.1% | not standardized |
| Sulfate (SO4) | ≤ 0.01% | ≤ 0.2% | not standardized |
| Heavy metals as Pb | ≤ 10 mg/kg | ≤ 20 mg/kg | ≤ 50 mg/kg |
| Loss on drying | ≤ 0.5% | ≤ 1.0% | ≤ 1.5% |
Representative commercial release ranges are shown; supplier specifications vary by manufacturing route and analytical method.
Because the high-purity anhydrous powder dissolves rapidly in water—reported solubility approximately 85 g per 100 mL at 25 °C—it can be incorporated into liquid mineral supplements without the grinding step required for insoluble selenium sources. In dry premix manufacture, the powder is typically blended into a carrier such as calcium carbonate or wheat middlings and then diluted into complete feed. The critical regulatory boundary is not the purity of the sodium selenite alone but the final added selenium concentration in the complete feed; under 21 CFR 573.920, sodium selenite is an approved selenium source for food-producing animals, and added selenium is generally limited to 0.3 mg/kg in complete feed for major production species. A high-purity grade does not relax this limit. It reduces the co-delivery of lead, cadmium, arsenic, and mercury at the premix inclusion level, which is material because selenium premixes are often included in mass fractions below 0.1% of the final feed, and concentrated trace impurities are therefore diluted only after blending. Batch-to-batch variance on production-scale ribbon mixers is controlled by assaying the premix before letdown and by using a coefficient of variation below 5% for selenium distribution in the finished feed. Where the premix is added to pelleted feed, the thermal and moisture conditions of conditioning should be reviewed; sodium selenite is water-soluble and can migrate toward the pellet surface if the mash contains excess moisture, but published data for this specific configuration is limited to internal mill records. The high-purity input lowers the analytical burden for heavy-metal release and reduces the chance of rejection under import limits that specify maximum lead and cadmium in trace-mineral products.
In soda-lime-silica glass manufacture, iron oxide impurities in silica sand and cullet impart a green transmission shade. Sodium selenite is introduced as a redox control agent and decolorizer: the selenium species released during melt decomposition compensates for the iron green by shifting the transmission spectrum toward neutral. The effective addition is small and process-dependent, typically metered in the range of 10 g to 100 g elemental selenium equivalent per tonne of glass batch; over-addition produces a pink or amber-grey cast, while under-addition leaves residual green. Process engineers adjust the dose by transmission spectrophotometry across 400 nm to 700 nm and by oxidizing or reducing furnace conditions, not by batch chemistry alone. High-purity material is preferred in this application because chloride, sulfate, and lead can influence fining behavior, refractory corrosion, and glass compliance with packaging-contact regulations. Cross-fired regenerative furnaces with throughputs above 200 tonnes/day may exhibit residence-time distributions that amplify color variability when the selenite particle size distribution shifts; for this reason, tight control of particle size below 250 μm and predrying of the powder are typical in glass plants. The selenite is normally fed through a minor-ingredient weighing station after the main batch mixer, and the weighment is verified to within ±2% of target to avoid color drift. Published data for specific furnace configurations is limited because optimizations are often proprietary, but the use of a high-purity input reduces the uncontrolled import of sulfate and chloride that can otherwise alter the oxidation state of the melt.
In controlled laboratory synthesis of selenium-containing organic molecules and selenoproteins, the anhydrous high-purity reagent is used as a stoichiometric selenium source because residual sulfate and chloride are constrained below 0.01% and 0.005%, respectively, thereby reducing side reactions in thiol-disulfide exchange and electrophilic aromatic substitutions. Sodium selenite is a mild oxidant and can be reduced to elemental selenium by ascorbic acid, hydrazine, or sodium borohydride; the reduction pH, normally held between 5.5 and 6.5 for ascorbic acid routes, controls particle nucleation and final colloidal size. In buffer preparations and microbiological media, the high-purity product provides selenium in the +4 oxidation state without introducing phosphate or chelating agents that interfere with downstream proteomic analysis. The compound should not be combined with strong reducing agents or combustible organic materials in the dry state; acidic conditions generate selenious acid, and contact with concentrated hydrochloric acid in the presence of reducing impurities can generate volatile selenium species. For synthetic reproducibility, users typically standardize stock solutions by iodometric titration or inductively coupled plasma mass spectrometry and store them in high-density polyethylene containers away from light. The high-purity grade is also used in preparation of selenite-based standards for calibration of atomic fluorescence and hydride-generation atomic absorption instruments, where the absence of chloride and sulfate reduces spectral interferences during hydride formation.
Compendial and regulatory acceptance for sodium selenite varies by application. In pharmaceutical or dietary supplement contexts, the relevant elemental impurity risk is evaluated under ICH Q3D or the monograph limits of the applicable pharmacopoeia. High-purity grades are not automatically compliant with every pharmacopoeial monograph; the certificate of analysis must confirm that the elemental impurity profile meets the monograph’s specific limits for lead, arsenic, cadmium, and mercury, and that the assay is performed by the prescribed redox titration or equivalent method. Feed applications require compliance with the source and labeling conditions of 21 CFR 573.920, and most jurisdictions require the product to be registered as a feed additive before import. The table below summarizes the main compliance anchors for high-purity sodium selenite in different use environments.
| Use environment | Primary standard or regulation | Typical controlled parameter |
|---|---|---|
| Animal feed premix | 21 CFR 573.920 | Added selenium ≤ 0.3 mg/kg complete feed for major production species |
| Food chemical use | FCC sodium selenite monograph | Assay 98.0%–101.0%; lead limit per monograph |
| Pharmaceutical/laboratory use | ICH Q3D | Elemental impurity limits based on permitted daily exposure |
| Glass packaging contact | EU Regulation 1935/2004 and applicable national positive lists | Migration of selenium and heavy metals measured in food simulants |
Release testing for high-purity sodium selenite should include assay, loss on drying, water-insoluble matter, chloride, sulfate, selenate, and the full elemental impurity panel. The most common assay procedure is iodometric titration after dissolution, while selenium content is confirmed by inductively coupled plasma mass spectrometry or hydride-generation atomic absorption spectrometry. Anions are quantified by ion chromatography using ISO 10304-1 or an equivalent method; loss on drying is performed according to USP 731 or Ph.Eur. 2.2.32. Particle-size distribution is measured by laser diffraction under ISO 13320, and oversized material is removed by sieving or air classification. For high-purity product used in feed or pharmaceutical applications, the certificate of analysis should also include a statement of the analytical method used for heavy metals and the detection limits attained. A high-purity lot should not be accepted solely on the basis of a generic “99%” label; the impurity profile, not the selenium assay, is the controlling specification in most high-value uses.
In architectural metal finishing, dilute sodium selenite solutions are used to produce black and grey conversion coatings on copper and copper alloys. The high-purity product is preferred because chloride contamination above 0.005% can induce localized pitting, while sulfate and heavy metals alter the final patina hue. Process baths are typically maintained at 20 °C to 30 °C with immersion times from 30 s to 120 s; the selenite acts as a mild oxidant and selenium source, depositing a mixed copper-selenium oxide film. Bath stability is monitored by pH and specific gravity, and replenishment is based on redox titration rather than visual appearance alone. The performance of the conversion coating should be validated by neutral salt spray testing under ISO 9227 or cyclic corrosion testing under ISO 11997-1 before field deployment, because published data for this specific configuration is limited to supplier technical bulletins. High-purity sodium selenite is also used in some steel blackening processes, where it is combined with phosphoric acid and copper salts; in these baths, chloride and sulfate control is critical to avoid sludge formation and non-uniform color.
In storage and handling, the anhydrous powder is hygroscopic and should be kept sealed in high-density polyethylene drums with low-moisture barrier liners; at relative humidity above 60%, surface wetting and caking increase the risk of weighing errors and dust adhesion. Because the oral and inhalation toxicity of selenium compounds is high, dust generation during transfer is controlled by local exhaust ventilation and by the use of sealed bag-in-box stations in production areas. The product is incompatible with strong reducing agents, acidic media in the presence of organic matter, and direct contact with oxidizable powders such as ascorbic acid or hydrazine salts if mixed in concentrated form. For processes requiring low moisture, the material may be dried at 40 °C to 60 °C under vacuum before use; published data for this specific configuration is limited, and the certificate of analysis should be consulted for the lot-specific volatiles content.