| HS Code | 250274 |
| Chemical Name | Sodium selenite |
| Chemical Formula | Na2SeO3 |
| Molecular Weight | 172.94 g/mol (anhydrous) |
| Cas Number | 10102-18-8 |
| Grade | Laboratory grade |
| Appearance | White crystalline powder |
| Purity | ≥98% |
| Solubility | Soluble in water; slightly soluble in ethanol |
| Melting Point | Decomposes above 320°C |
| Density | 3.1 g/cm3 at 20°C |
| Ph | Aqueous solution is slightly alkaline |
| Storage Conditions | Store tightly closed in a cool, dry area, away from acids and reducing agents |
| Hazards | Toxic, harmful if swallowed, dangerous to the environment |
As an accredited Sodium Selenite Laboratory Grade factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 500 g bottle of Sodium Selenite Laboratory Grade, white crystalline powder, tightly sealed with hazard labeling for safe handling. |
| Container Loading (20′ FCL) | 20′ FCL of Sodium Selenite Laboratory Grade: packed in sealed drums, palletized, secured, and labeled for safe transport. |
| Shipping | Sodium Selenite Laboratory Grade ships as a hazardous, toxic solid in sealed, corrosion-resistant containers, clearly labeled with UN2630 and hazard warnings. It must be kept dry, away from acids and incompatibles. Transport requires compliant packaging, documentation, and trained handlers per dangerous goods regulations. |
| Storage | Store sodium selenite laboratory grade in a cool, dry, well-ventilated area, in a tightly sealed, clearly labeled container protected from light and moisture. Keep away from acids, oxidizing agents, and incompatible materials. Use secondary containment to prevent spills, and restrict access to trained personnel due to its toxicity. |
| Shelf Life | Store tightly closed in a cool, dry place. Shelf life is typically three years when protected from light and moisture. |
In container glass decolorizing, anhydrous sodium selenite laboratory grade is introduced as a selenium donor rather than as a direct colorant. The salt undergoes thermal decomposition in the batch blanket below 710 °C to release SeO₂, which is subsequently reduced in the melt to polyselenide and selenide species. The complementary pink-red absorption band from 480 nm to 540 nm offsets the green transmission from FeO, but the correction is effective only when the FeO/Fe₂O₃ ratio is held within a narrow range. Batch oxygen demand is controlled with sodium nitrate additions of 0.5–2.0 kg/t sand and carbon additions of 0.05–0.20 kg/t sand in regenerative end-port furnaces operating at crown temperatures of 1,450–1,550 °C. Production-scale observations on end-port furnaces show selenium retention falling below 20% when the batch redox number exceeds +10, while retention above 50% is encountered only with cullet ratios above 60% and short furnace pull rates. Dispersion is process-critical: a 1:50 pre-blend of sodium selenite in dry silica sand or dense soda ash reduces localized over-reduction and eliminates selenium speck defects on the cold end. Direct addition into the doghouse without pre-blending can produce transient Se concentrations above 0.05 wt%, forming amber-brown colloidal selenium streaks in the ribbon.
The stock addition rate for selenium-based decolorizing in soda-lime container batches ranges from 0.0005 wt% to 0.003 wt% Se on finished glass, corresponding to 0.011–0.066 kg/t anhydrous sodium selenite. For selenium-tinted bronze or grey glass, the target selenium content rises to 0.005–0.020 wt%; for ruby glass, selenium is loaded at 0.05–0.30 wt% and is normally co-precipitated with cadmium sulfoselenide rather than supplied as sodium selenite alone. Finished-glass selenium content is verified by wavelength-dispersive X-ray fluorescence using matrix-matched standards prepared per ASTM E1621-22, and color coordinates are reported according to ISO 11664-4:2008. On the batch-house floor, exposure is governed by national occupational exposure limits such as the OSHA PEL of 0.2 mg/m³ for selenium compounds; baghouse capture systems should maintain an air-to-cloth ratio not exceeding 1.2 m/min, and acid-resistant aramid filter bags are preferred because selenium oxides in humid air form acidic leachates that hydrolyze standard polyester media.
The formulation inputs below are expressed as retained Se in finished glass; actual raw batch loading must be recalculated upward when furnace retention is below the values shown.
| Glass type | Batch sodium selenite loading | Finished selenium concentration | Critical melt control parameter |
|---|---|---|---|
| Decolorized soda-lime container | 0.011–0.066 kg/t | 0.0005–0.003 wt% Se | Batch redox number below +10 |
| Selenium-tinted bronze/grey | 0.110–0.438 kg/t | 0.005–0.020 wt% Se | FeO/Fe₂O₃ ratio stabilized by sulfate/carbon balance |
| Ruby glass | 1.095–6.571 kg/t | 0.05–0.30 wt% Se | Cadmium sulfoselenide co-feed and reducing atmosphere |
Finished-product categories supplied from these furnaces include colorless flint container glass, architectural float glass, bronze and grey tinted glazing, and selenium-ruby tableware, each requiring a separate furnace color calibration because cullet color contamination shifts the dominant wavelength by more than 5 nm after a product changeover.
Sodium selenite laboratory grade enters feed premix production as a water-soluble inorganic selenium source, but its potency creates a formulation hazard if the first dilution is not mechanically verified. The selenium fraction of anhydrous sodium selenite is 45.65 wt%, so a 0.5% Se premix requires 10.95 g of sodium selenite per kg of carrier. At the complete-feed stage, a 100 g/t inclusion of this 0.5% premix delivers 0.5 mg/kg Se, matching the EU maximum total selenium for complete feed at 12% moisture under Regulation (EC) No 1831/2003. For U.S. formulations covered by 21 CFR 573.920, the same premix is restricted to 60 g/t, supplying 0.3 mg/kg Se for chickens, turkeys, swine, sheep, and cattle. Serial dilution is performed in a double-ribbon batch mixer with a paddle tip speed of 1.2–1.8 m/s; the active salt is first expanded 1:10 into calcium carbonate or rice hull carrier, screened through a 250 µm sieve, and then expanded again to the final 1:100 or 1:1000 premix. Homogeneity is accepted only when the coefficient of variation for selenium in 20 sampling points falls below 5% using hydride-generation ICP-OES after closed-vessel digestion.
Post-mixing segregation is the main production bottleneck. In low-moisture premixes below 8% moisture, fine sodium selenite particles acquire electrostatic charge, adhere to stainless-steel mixer walls, and release irregularly into later batches; this is controlled by grounding the mixing equipment and limiting final blend storage to 72 h before use. The compound is chemically incompatible with ascorbic acid and reducing monosaccharides in the same concentrated premix, because partial reduction to elemental selenium produces grey speck and lowers bioavailable selenium. Under pelleting conditions of 80–85 °C and 1.5–2.5 bar steam pressure, sodium selenite remains analytically stable, but dry mixing before steam conditioning must achieve full dilution because localized wetting of concentrated selenite at the conditioner inlet causes caking on the first-flight auger. Terminal feed types produced under this protocol include layer and broiler rations, nursery pig feeds, dairy transition cow mineral packs, and extruded aquafeed sinking pellets, each adjusted by final targeted selenium intake rather than by fixed premix inclusion.
| Market | Regulatory reference | Total selenium ceiling in complete feed |
|---|---|---|
| United States | 21 CFR 573.920 | 0.3 mg/kg for approved species |
| European Union | Regulation (EC) No 1831/2003 | 0.5 mg/kg at 12% moisture |
Preparation of Se(IV) calibration standards from sodium selenite laboratory grade requires a mass-fraction purity correction rather than direct assumption of stoichiometric selenium content. The salt dissolves without turbidity in 2% HNO₃ at 20 °C; a stock solution containing 1,000 mg/L Se is produced by dissolving 2.190 g anhydrous sodium selenite per litre, but laboratory-grade material is standardized against NIST SRM 3149 or a traceable Se(IV) certified reference material because certificates of analysis typically report assay only in the range 98.0–99.5%. Working standards of 0.5–100 µg/L Se should be prepared daily by serial dilution in PFA volumetric ware; storage in borosilicate glass at 4 °C leads to low-level adsorption onto the vessel surface after 72 h, whereas PFA containers with sub-boiled nitric acid at pH below 2.0 maintain Se(IV) stability for 14 days. This is important for ICP-MS calibration under ISO 17294-2:2016 and for hydride-generation AAS under ISO 9965:1993, where the blank response must remain below 0.1 µg/L Se to support a level of quantification near 0.5 µg/L.
Metrological traceability in routine testing is governed by ISO/IEC 17025:2017 clause 6.5; the laboratory reagent is therefore not considered a primary reference source unless the batch has been characterized by isotope-dilution ICP-MS against a higher-order CRM. In downstream analytical production, spiked matrix QC samples at 10 µg/L and 50 µg/L are processed through closed-vessel microwave digestion with HNO₃/H₂O₂ at 180 °C; recoveries outside 85–115% invalidate the digestion batch. For selenium speciation, sodium selenite is the appropriate Se(IV) standard, but oxidation to Se(VI) in high-pH or peroxide-containing mixed standards must be monitored with anion-exchange HPLC-ICP-MS; published data for fractional conversion in ambient, multi-element standard mixtures is limited, and each laboratory must validate its own expiry interval. Terminal products produced with this reagent include in-house calibration solutions, matrix spike concentrates for environmental and food analyses, and proficiency-testing specimens for arsenic-selenium panel schemes.
In architectural brass and bronze finishing, cold blackening baths have historically been formulated from selenious acid, but anhydrous sodium selenite laboratory grade can be converted in situ by adding the stoichiometric equivalent of hydrochloric or nitric acid under controlled extraction. A typical immersion bath contains 10–30 g/L sodium selenite, 5–15 mL/L concentrated HCl, and 2–10 g/L cupric sulfate; bath temperature is held at 20–35 °C and immersion time ranges 60–300 s depending on copper alloy composition. The coating mechanism is a galvanic displacement reaction in which selenite species are reduced on copper-rich surfaces to copper selenide and elemental selenium, producing an adherent black conversion film with thickness 0.2–1.5 µm. Production-scale immersion lines require filtered solution circulation at 4–6 tank volumes per hour and a separate drag-out rinse, because selenite-laden drag-out entering an alkaline cleaner precipitates selenium sludge that blocks spray nozzles. The process is not suitable for aluminium, zinc die-cast, or high-nickel alloys; published data for leaded brass with Pb above 2.5% is limited, and pitting appears when immersion exceeds 5 min.
Wastewater treatment for selenium from cold blue lines uses ferrous sulfate co-precipitation at pH 8.5–9.5, followed by sand filtration and analysis by EPA 200.8 or ISO 17294-2:2016; site discharge permits are set under EU Industrial Emissions Directive 2010/75/EU or U.S. categorical standards in 40 CFR Part 433 for metal finishing wastes. The terminal product range includes blackened brass door hardware, bronze plaques, optical instrument barrels, and firearm sight components, where the selenite-derived film must pass a 90° bend adhesion check and neutral salt-spray exposure of 24 h without red rust under ISO 9227:2022. Bath life is typically limited by accumulation of copper sulfate reaction products; drag-out of dissolved copper beyond 25 g/L shifts the deposit toward brown, requiring partial decanting and replenishment with fresh sodium selenite rather than simple acid addition.
Sodium selenite laboratory grade serves as the water-soluble selenium source in the coprecipitation of cadmium sulfoselenide pigments, where the CdSe:CdS molar ratio determines the visible reflectance edge between orange and deep red. In a sealed precipitation reactor, aqueous cadmium sulfate is combined with separately metered sodium selenite, sodium sulfide, and sodium hydroxide at 60–80 °C; pH is held at 9.5–11.5 to control nucleation and particle growth. The precipitated cake is filtered, washed to conductivity below 500 µS/cm, dried at 120 °C, and calcined in refractory saggars under a nitrogen atmosphere at 550–700 °C for 2–6 h. Sodium selenite addition is calculated from the target selenium fraction: for a ruby-red CdSe0.6S0.4 chromophore, selenium represents 27.45 wt% of the inorganic pigment, requiring approximately 0.60 kg sodium selenite per kg of pigment after filtration and calcination losses. Over-addition above 5% of the stoichiometric selenium shifts the hue toward brown and produces free selenium efflorescence on the glaze surface.
Ceramic food-contact glazes containing cadmium sulfoselenide pigments must meet cadmium and lead migration limits under ISO 6486-1:2019, with cadmium release from the fired article typically required below 0.3 mg/L for flatware and 0.1 mg/L for small hollowware depending on regulatory jurisdiction and intended market. The pigment is not acid-fast; in glaze systems with pH below 4.5, the sulfoselenide lattice degrades and releases odorant hydrogen selenide during firing. Zinc-free frits are specified because zinc sulfide formation decolorizes the red toward buff. Terminal product categories include ceramic tableware glazes, architectural glass enamels, ceramic decals, and studio ceramic colorants, each fired in oxidation or neutral kiln atmospheres not exceeding 1,050 °C for cadmium sulfoselenide reds to avoid sublimation losses.
At the µg-scale inclusion rates used for dietary selenium fortification, direct compression blending requires a disciplined geometric dilution sequence because the active dose is below the flowability threshold of tableting excipients. Sodium selenite is listed as a permitted selenium source for food supplements under Directive 2002/46/EC, Annex II. A tablet delivering 55 µg selenium requires 0.120 mg anhydrous sodium selenite; a 200 µg tablet requires 0.438 mg, based on the 45.65% selenium content. The active is first blended 1:1000 with dicalcium phosphate or microcrystalline cellulose in a V-blender operated at 60% fill, 15 rpm, and 25 min mixing time; a second 1:10 expansion brings the selenium concentration into the working range for a rotary tablet press. Final blend uniformity is tested according to USP <905> with an acceptance value not greater than 15.0. Direct compression is applied at 8–15 kN compression force on a 12-station rotary press, and selenium content in finished tablets is assayed by ICP-MS after microwave digestion per USP <2232> with a recovery window of 90–110%.
Process boundaries are narrow. Anhydrous sodium selenite is hygroscopic and agglomerates above 60% relative humidity; pre-dried excipients and a dehumidified compression suite are required to prevent picking on the tablet tooling. Direct contact with ascorbic acid at concentrations above 100 mg per tablet is avoided because Se(IV) reduces to elemental red selenium, visible as pink speck in the tablet matrix and detectable as a drop in water-soluble Se(IV). Cleaning of blending and tableting equipment after a sodium selenite campaign uses 0.1 M NaOH rinse followed by water and drying, with rinse-water selenium monitored below 10 µg/L prior to disposal. Terminal products include single-entity selenium tablets, selenium-containing multivitamin-mineral tablets, two-piece capsules filled from the pre-blend, and powdered supplement sachets where the premix is dry-mixed with flavor carriers; published data for long-term selenium stability in effervescent matrices at low pH is limited, and such formulations require separate stability confirmation.
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Sodium selenite laboratory grade is supplied as a white crystalline solid with the anhydrous form CAS 10102-18-8 and the pentahydrate Na2SeO3·5H2O CAS 26970-82-1. The pentahydrate has a formula weight of 263.02 g/mol and contains 30.0% selenium by mass, whereas the anhydrous salt has a formula weight of 172.94 g/mol and contains 45.7% selenium by mass. Laboratory grade material is not a single specification; the designation indicates controlled purity for general laboratory use, falling between technical grade and ACS reagent grade in trace-metal documentation. Model designations in common distribution channels are tied to packaging size and hydration state rather than to an intrinsic chemical difference; pack sizes include 100 g, 500 g, and 2.5 kg units of the pentahydrate. The material is used in selective microbiology media, Se(IV) reagent preparation, and synthetic transformations where selenium oxidation state must be fixed.
The specification boundary is defined primarily by the assay and anion profile, not by hydration state. Laboratory grade sodium selenite commonly carries an assay of ≥98.0% Na2SeO3 on an anhydrous basis and permits selenate, chloride, and sulfate at levels that vary by supplier; technical grade may contain insoluble residues and higher heavy-metal burdens from ore-derived selenium. Technical grade material also may show a gray or pink cast from elemental selenium decomposition, which reduces the effective soluble Se(IV) concentration. ACS reagent material, where available, is controlled under the American Chemical Society reagent specifications and includes additional tests for trace substances that laboratory grade lots may not include. Users performing trace-selenium speciation should not assume that laboratory grade is interchangeable with high-purity standards; lot-specific certificates of analysis govern every decision.
| Parameter | Sodium selenite laboratory grade pentahydrate | Sodium selenite anhydrous | Sodium selenate |
|---|---|---|---|
| CAS registry number | 26970-82-1 | 10102-18-8 | 13410-01-0 |
| Formula | Na2SeO3·5H2O | Na2SeO3 | Na2SeO4 |
| Formula weight | 263.02 g/mol | 172.94 g/mol | 188.94 g/mol |
| Selenium content | 30.0% | 45.7% | 41.8% |
| Selenium oxidation state | +4 | +4 | +6 |
| Representative laboratory use | Selective broth preparation; Se(IV) synthesis | Gravimetric standards where water interferes | Comparative studies; oxidative systems |
Because sodium selenite is water-soluble and mildly alkaline in solution due to selenite ion hydrolysis, dissolution in ASTM D1193 Type II reagent water yields clear solutions. The laboratory grade material is not certified for food or drug use; feed-grade sodium selenite is regulated separately under 21 CFR 573.920. Selection of the pentahydrate versus anhydrous form is governed by whether residual water affects stoichiometric calculations.
In inductively coupled plasma mass spectrometry, sodium selenite laboratory grade is not a primary certified reference material, but it can be used to prepare matrix spike solutions when its assay and selenate content are known. A 1000 mg/L Se(IV) stock solution is prepared by dissolving 3.33 g of the pentahydrate in 1 L of 1% HNO3; because the salt contains 30.0% selenium by mass, not all of the weighed mass is selenium. The solution should be checked against a certified Se(IV) standard using inductively coupled plasma optical emission spectrometry or isotope dilution mass spectrometry before use. This configuration is stable for 30 days when stored in HDPE at 2–8 °C; longer storage may result in adsorption or redox shifts. Users should not use laboratory grade powder as a calibrant without independent concentration verification because the salt is hygroscopic and may have variable hydration.
Selective enrichment broth preparations employ sodium selenite as a redox-active bacteriostatic agent. A typical selenite cystine broth formulation includes sodium selenite at approximately 4 g/L. Salmonella spp. tolerate the selenite concentration and reduce Se(IV) to red elemental selenium, while many competing gram-positive cocci and enteric non-target organisms are suppressed. Inclusion of lactose at approximately 4 g/L and sodium phosphate at 10 g/L buffers the medium; fermentation of lactose by non-target organisms lowers pH, but the phosphate buffer limits acid inhibition of Salmonella. Process control is narrow: autoclaving the complete medium drives premature reduction of selenite to elemental selenium, reducing selectivity, so the base mixture is dissolved with gentle heat and used without terminal sterilization in the enrichment step. Incubation at 35 °C ± 2 °C for 18–24 h is common, with subculture onto selective agars. Selectivity is highest during the first 12–18 h; prolonged incubation beyond 24 h allows non-target organisms to recover. Subculture should occur from the upper third of the broth, avoiding settled red selenium that may carry adsorbed cells. Performance testing follows ISO 11133:2014, using Salmonella Typhimurium ATCC 14028 and Salmonella Enteritidis ATCC 13076 as productivity strains and Enterococcus faecalis ATCC 29212 or Escherichia coli ATCC 25922 as selectivity strains. When a laboratory substitutes a different grade of sodium selenite, the redox potential and anion impurities can shift the inhibition window; a lot-specific verification should be performed before routine use. Published data for this specific configuration is limited outside compendial media studies, so operators should verify performance under their own ISO 11133 quality controls and the applicable national reference method such as ISO 6579-1:2017 where required.
The pentahydrate form loses water slowly if stored above 40 °C or in unsealed containers, and gravimetric preparation of 0.1 M Se(IV) stock solutions should assume the label hydration state only after confirming lot-specific assay. A 0.1 M sodium selenite pentahydrate solution requires 26.3 g per liter, while the anhydrous salt requires 17.3 g per liter. Confusion between hydration states produces a 52% relative error in selenium concentration. For ICP-OES calibration, stock solutions prepared from sodium selenite should be acidified with 1% HNO3 and stored in HDPE containers to reduce adsorption. For hydride-generation atomic absorption spectrometry, Se(IV) is derivatized to H2Se by sodium borohydride in 6 M HCl; Se(VI) requires pre-reduction with hydrochloric acid and heat. This distinction makes selenate contamination in sodium selenite a practical issue, not a theoretical one. Selenium(IV) in aqueous solution may undergo reduction to Se(0) if untreated sample matrices contain sulfide or ascorbic acid; spike recovery below 80% indicates matrix-induced redox loss rather than analytical instrument drift. Operators should verify solution stability with a certified selenium reference material over the same run.
Certificate-of-analysis documentation for laboratory grade sodium selenite pentahydrate typically reports assay, selenate, chloride, sulfate, and water content. Representative acceptance limits for a commercial lot may include assay ≥98.0%, selenate ≤0.5%, chloride ≤0.01%, sulfate ≤0.05%, and heavy metals as Pb ≤0.005%. These limits are not universal; they vary between distribution channels and must be checked against the actual CoA. The certificate may also report loss on drying and water content by Karl Fischer titration. The selenate level is operationally important because selenate is the Se(VI) analogue and can alter redox-dependent applications. In microbiology, selenate is less selective than selenite for Salmonella enrichment, so oxidation of selenite to selenate lowers the effective selective sodium selenite concentration. In analytical work, the presence of selenate requires speciation to avoid misassignment of Se(IV) and Se(VI) peaks when using hyphenated techniques.
Reductive precipitation of Se(IV) to elemental selenium proceeds readily with ascorbic acid, hydrazine sulfate, or sodium borohydride under ambient conditions. In a typical laboratory preparation, sodium selenite laboratory grade is dissolved to 0.01–0.10 M in purified water, and the reducing agent is added dropwise until the solution develops a red-orange colloidal appearance; the product is amorphous Se(0) with particle size controlled by stirring rate, temperature, and precursor concentration. Stirring at 500–800 rpm with a magnetic stirrer yields a narrower particle-size distribution than stagnant reduction. Stable colloids require capping agents such as polyvinylpyrrolidone or citrate. For synthesis of organoselenium compounds, sodium selenite is acidified to selenious acid before reaction with aromatic amines or hydrazines; published data for this specific configuration is limited, and yields depend on the exclusion of atmospheric oxygen. Use of laboratory grade rather than technical grade reduces side reactions from transition-metal impurities that can catalyze undesired oxidation. However, the material is not suitable as a certified standard for trace selenium without independent assay.
Because sodium selenite is hygroscopic and oxidizing, bulk mixing of dry culture media should be conducted in a humidity-controlled room below 60% RH. Sodium selenite should not be mixed with acidic components or strong reducing agents in concentrated form, because acidification can produce selenious acid and reducing agents generate hydrogen selenide or elemental selenium. The material is classified under GHS as toxic if swallowed and very toxic to aquatic life with long-lasting effects; typical hazard statements include H301, H331, and H410. Occupational exposure limits for selenium compounds are commonly 0.2 mg/m3 as Se for the respirable fraction; local exhaust ventilation and periodic air monitoring are standard controls. Engineering controls include local exhaust ventilation for powder transfer and the use of nitrile gloves. Spilled powder should be collected without dry sweeping to limit dust generation. Waste solutions containing selenite are managed separately from general laboratory drain disposal because selenium discharge limits in receiving waters are commonly below 0.05 mg/L. Incompatibilities include strong acids, aluminum powder, and strong reducing agents such as zinc dust or lithium aluminum hydride. For long-term storage, the container should be kept in a cool, dry, dark area, and opened containers should be resealed under dry nitrogen if the anhydrous form is used.