Product Overview
Sodium Bisulfite 25% Solution is a ready-to-use reducing agent supplied in technical grade for industrial dechlorination, textile bleach reduction, and chemical synthesis. The active species — sodium hydrogen sulfite (NaHSO₃) — donates electrons rapidly in aqueous systems, making it a workhorse wherever dissolved oxidants need to be knocked down before discharge, dyeing, or downstream reaction.
This solution is offered in sizes from 1-quart bottles through 330-gallon totes, so it scales from bench trials to continuous-feed process loops. Technical grade is the standard pick for water-treatment plants, textile mills, and chemical intermediates operations where analytical-grade purity is unnecessary and cost per pound matters.
Why This Concentration
A 25% aqueous solution strikes the balance between handling ease and useful activity. At this strength the liquid is dilute enough to meter through standard chemical-feed pumps and in-line injectors without the corrosion concerns that come with concentrated bisulfite, yet concentrated enough that reasonable feed rates still deliver the stoichiometric demand of most dechlorination or reducing steps. Operators avoid the dust and dissolution time of dry sodium bisulfite powder, and the pre-dissolved form means no undissolved solids to clog metering equipment.
Technical grade at 25% is the specification most municipal and industrial water-treatment operators write into their SOPs for dechlorination — the reducing power is predictable, the solution density is close enough to water for volumetric metering, and the lower concentration reduces the intensity of sulfur dioxide off-gassing during transfers compared to stronger solutions.
Chemical Profile
Sodium Bisulfite 25% Solution presents as a clear, colorless to light-yellow liquid with a slight sulfur dioxide odor characteristic of the bisulfite ion in solution. Its density falls in the range of approximately 1.18–1.22 g/cm³ at 20 °C, reflecting the dissolved salt load. The solution is fully miscible with water at all proportions, which is why it integrates directly into aqueous process streams without emulsification or co-solvents. The molecular formula is HNaO₃S with a molecular weight of 104.06 g/mol, registered under CAS 7631-90-5.
Industrial Applications
Sodium bisulfite solution serves as a reducing agent across several distinct industrial workflows. Each application leverages the same core chemistry — the bisulfite ion's ability to donate electrons and scavenge dissolved oxidants — but the operational context differs.
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Dechlorination in water treatment. After disinfection, municipal and industrial discharge permits typically require free chlorine to be reduced below detectable limits before effluent enters a receiving waterway. Sodium bisulfite reacts with hypochlorous acid and hypochlorite ion to form chloride and sulfate, eliminating residual chlorine without introducing persistent organic byproducts. Operators inject the 25% solution downstream of the chlorine contact chamber through a metering pump calibrated to the chlorine residual.
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Textile processing. In bleaching and dyeing operations, fabrics treated with chlorine- or peroxide-based bleaches carry residual oxidant that can interfere with subsequent dye uptake. A bisulfite rinse neutralizes that residual, giving the dye bath a clean, uniform substrate. The reducing action also strips certain vat dyes during color-correction steps.
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Chemical intermediate. Sodium bisulfite participates as a reactant or reducing agent in the synthesis of dyes, sulfonated compounds, and other downstream chemicals. Its aqueous form simplifies metering into batch reactors and continuous-flow systems.
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Oxygen scavenging. In boiler feedwater conditioning and closed-loop cooling systems, dissolved oxygen accelerates corrosion of steel internals. Bisulfite solution reduces dissolved O₂ to water, extending equipment life in systems where catalyzed sulfite programs are specified.
Handling & Storage
Sodium bisulfite solution carries the signal word Danger (per the product's GHS classification). The governing hazard statements are: H302 — Harmful if swallowed; H318 — Causes serious eye damage; EUH031 — Contact with acids liberates toxic gas (per the product's GHS classification). That last point is operationally critical: if bisulfite contacts mineral acids, sulfur dioxide gas is released. Never store or pipe this product alongside hydrochloric, sulfuric, or nitric acid lines without an engineered separation.
PPE for transfers and connections includes chemical splash goggles (not safety glasses — the H318 eye-damage statement demands sealed eye protection), chemical-resistant gloves rated for sulfite solutions, and a face shield when breaking connections on drums or totes. Work in ventilated areas or use local exhaust to manage the slight SO₂ off-gassing during open transfers.
Store containers sealed, upright, in a cool area away from direct sunlight and heat sources. HDPE drums and IBC totes are the standard containment materials. Avoid strong oxidizing agents in the same storage bay — bisulfite is a reducing agent and will react. Shelf life is longest when containers remain sealed; once opened, minimize headspace to slow aerial oxidation of bisulfite to sulfate.
Hazmat & Shipping
Sodium Bisulfite 25% Solution ships as a regulated hazardous material under DOT. The transport classification details, as printed on the shipping papers that accompany every shipment:
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UN Number: UN2693 (per 49 CFR 172.101)
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Hazard Class: 8 — Corrosive (per 49 CFR 172.101)
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Packing Group: III (per 49 CFR 172.101)
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Proper Shipping Name: Bisulfites, aqueous solutions, n.o.s. (Sodium bisulfite) (per 49 CFR 172.101)
Class 8 / PG III indicates a corrosive material at the lowest severity tier within that class, but it still requires full hazmat documentation, placarding on bulk shipments, and a trained hazmat shipper. Alliance Chemical holds USDOT registration 2188383 and ships Class 8 materials from our Taylor, TX facility as a routine part of daily operations.
Documentation
A Safety Data Sheet (SDS) ships with every order, available in English, Spanish, French, and Japanese. Lot-specific Certificates of Analysis (COA) are available on request and confirm the assay and key quality parameters of the specific production lot you receive. A Technical Data Sheet (TDS) is also available for process-engineering reference.
Why Buy from Alliance Chemical
This product is offered in sixteen size and packaging configurations — from a single quart for process trials up to 330-gallon totes for continuous-feed industrial systems — so you order the volume that fits your consumption rate without overbuying or repackaging. Alliance Chemical has operated as a chemical distributor since 1998, serving over 50,000 customers across industrial, municipal, and institutional markets. Shipping and handling guidance for this product is reviewed by Andre Taki, DOT Hazmat Specialist.
