Ammonium Thiosulfate Storage — HDPE ATS Liquid Fertilizer Tank Guide

Ammonium Thiosulfate Storage — (NH₄)₂S₂O₃ Tank System Selection

Ammonium Thiosulfate ((NH₄)₂S₂O₃, CAS 7783-18-8) is a dominant liquid sulfur-delivery fertilizer (12-0-0-26S) in US row-crop agriculture with three critical specification rules: keep below 120°F to prevent decomposition, segregate from strong acids to prevent hydrogen-sulfide release, and exclude copper and brass from wetted service to prevent copper-sulfide precipitation widely used across industrial, municipal, food, and specialty-chemical applications. This page consolidates the material-compatibility, regulatory hazard communication, storage-protocol, and field-handling reality for specifying a tank system that holds Ammonium Thiosulfate safely over a 20-year service life.

The six sections below work in order from resin-level compatibility through hazard communication, storage protocol, and operator-scale FAQs. Citations reference FDA, OSHA, NFPA, EPA, and manufacturer resistance charts; no resin codes are fabricated — where a borderline rating exists, the text defers to the manufacturer chart.

Ammonium Thiosulfate Compatibility Matrix — 12-0-0-26S Liquid Sulfur + Nitrogen Fertilizer

Ammonium thiosulfate (ATS, (NH₄)₂S₂O₃) is the dominant liquid sulfur-delivery fertilizer in US row-crop agriculture, sold almost exclusively as 12-0-0-26S aqueous solution at approximately 60% active concentration. It is also used in photographic fixer chemistry (historical volume, declining), gold and silver leaching (mining), and wet flue-gas desulfurization at coal-fired power plants (declining). ATS solution storage has three critical specification rules: (1) keep cool — ATS decomposes above 120°F to elemental sulfur and ammonium sulfate, and hot storage causes sulfur haze formation and tank-bottom sulfur deposits; (2) segregate from strong acids — acidification of thiosulfate releases hydrogen sulfide (H₂S) gas and SO₂, both toxic, with H₂S lethal at 100 ppm and detectable odor at 1 ppm (olfactory fatigue rapidly disables warning above 100 ppm); and (3) exclude copper, brass, and bronze — thiosulfate reacts with copper-alloy metals to form copper sulfide and can dissolve silver and copper significantly (this is the basis of photographic fixer chemistry). HDPE and XLPE are A-rated across the full ATS service range. The matrix reflects Tessenderlo Kerley ATS technical bulletin and TFI fertilizer handbook data.

The specification rule: HDPE or XLPE with 1.5+ SG rating for ambient ATS service, and scrupulous segregation from copper, acids, and heat sources. 316L stainless is a limited-service material due to thiosulfate-induced pitting and stress-corrosion-cracking susceptibility, particularly at weld seams and crevice joints — polyethylene is preferred. Aluminum is slowly attacked in dilute solution and aggressively attacked at concentration. Carbon steel is not used. Vinyl-ester FRP is acceptable. Elastomer gaskets: EPDM preferred; Viton and EPDM both acceptable at ambient; Buna-N limited. The 12-0-0-26S fertilizer-grade ATS solution has specific gravity 1.31–1.33, freeze point 14°F (crystalizes but recoverable), and a pH of 7.5–8.5.

Real-World Industrial Use Cases

US ammonium thiosulfate consumption is approximately 1.5 million short tons per year, dominantly agricultural:

• Row-crop liquid sulfur + nitrogen fertilizer (12-0-0-26S): The dominant use. Corn, wheat, canola, and alfalfa growers apply ATS as an in-row, side-dress, or broadcast spray for sulfur delivery alongside N-P-K blends. ATS is the preferred liquid sulfur source because it's fully miscible with UAN 32%, 10-34-0 (ammonium polyphosphate starter), and most common herbicides — no precipitation in tank mix. Dealer and applicator storage in 6,000–30,000 gallon HDPE or XLPE vertical flat-bottom tanks; farm-scale in 500–5,000 gallon HDPE storage and nurse tanks.
• UAN + ATS blends: Pre-blended N-S liquid fertilizers (e.g., UAN 28% + ATS blend delivering 20N-0P-0K-5S) are common at terminal-blending facilities, stored in 30,000–100,000 gallon XLPE or 316L stainless tanks.
• Herbicide safener / tank-mix adjuvant: ATS at 1–2 gallons per 100 gallons spray solution is occasionally used as a safener in sulfonylurea and triazine herbicide applications.
• Gold and silver leaching (mining): ATS is an emerging alternative to cyanide for gold and silver leaching in some mining operations, particularly where cyanide regulation is restrictive. Volume is limited but growing. Mining-site storage in 50,000–200,000 gallon HDPE or FRP leach-solution tanks.
• Photographic fixer (historical): ATS is the active ingredient in silver-halide photographic fixer baths — "hypo" in the darkroom trade. Declining volume with digital imaging displacement.
• Flue-gas desulfurization (FGD): Some wet FGD scrubbing chemistry uses ATS as a reductant for specific sulfur-capture chemistry. Declining volume.
• Dechlorination agent: ATS is a rapid-reducing agent for residual chlorine in industrial waste water and pool/spa water neutralization. Small-volume specialty use.

The standardized dealer-scale ATS installation is a 15,000–30,000 gallon HDPE or XLPE vertical flat-bottom tank, 1.5–1.9 SG rating, 3" or 4" bottom outlet, polymer fittings, atmospheric vent, and secondary containment. Shaded or north-facing tank siting is preferred to minimize summer solar gain. Total installed cost $12,000–$22,000. Critical specification callouts: no copper or brass fittings anywhere in the wetted path (copper alloys react to form copper sulfide within days), shaded or shelter siting in warm climates to keep bulk temperature below 95°F, and strict physical separation from acid storage (sulfuric acid, hydrochloric acid, acidic fertilizer) to prevent H₂S release in a co-mingled spill.

Hazard Communication — GHS, NFPA 704, DOT, Regulatory

CAS: 7783-18-8. UN: not regulated as hazmat. TSCA: listed, active. EINECS: 231-982-0.

• GHS pictogram: Exclamation mark (irritant). Signal word: Warning.
• GHS hazard statements: H315 (skin irritation), H319 (eye irritation), EUH031 (contact with acids liberates toxic gas — H₂S and SO₂).
• NFPA 704: Health 1, Flammability 0, Instability 1 (decomposes above 120°F to sulfur + ammonium sulfate), Special: none in default solution; becomes Health 3 if mixed with acid.
• DOT hazard class: not regulated as hazmat.
• EPA CERCLA RQ: not directly listed; H₂S release on acidification is CERCLA-reportable.
• SARA 302 EHS: not listed.
• DHS CFATS: not a Chemical of Interest.
• OSHA PEL for H₂S release: H₂S itself is 20 ppm ceiling (OSHA), 10 ppm TWA (NIOSH REL), IDLH 100 ppm.

ATS itself is a low-hazard commodity in routine handling — but the H₂S release potential in acid-contact scenarios is a serious operational hazard that drives most of the ATS-specific safety protocol. H₂S is lethal at 100 ppm, has a characteristic rotten-egg odor detectable at 1 ppm, but olfactory fatigue renders the warning smell ineffective above approximately 100 ppm — meaning workers can walk into a lethal H₂S plume without detecting it by smell. Gas-detection monitors (fixed and portable) are standard PPE at ATS bulk-handling and blending facilities. Acid spill scenarios involving ATS inventory have killed workers in multiple documented incidents at fertilizer terminals and farm storage sites over the past three decades. The segregation protocol is the single most important ATS safety rule: separate spill containment, separate piping, separate transfer pumps, and posted warning signs identifying the acid-segregation requirement. Decomposition above 120°F releases SO₂ (irritant, bleaching character) but not H₂S — the two hazard pathways are distinct.

Storage Protocol — HDPE Tank Design for ATS Liquid Fertilizer Service

Tank selection: HDPE or XLPE vertical flat-bottom with 1.5+ SG rating. Shaded siting or partial shelter preferred to limit bulk-solution temperature to below 95°F. Capacity 500–30,000 gallons. No copper, no brass, no bronze, no carbon steel. Aluminum not recommended.

Siting for temperature control: ATS decomposition accelerates above 120°F. Farm-scale outdoor installations in Gulf Coast, Southwest, and Southeast climates benefit from (1) natural-color polyethylene (less solar gain than black), (2) north-facing or shaded tank pad, (3) partial-shelter roof, and (4) summer-season tank-wall temperature monitoring with thermocouple or surface-mount temperature sensor.

Secondary containment: 110% of tank volume minimum. Lined concrete or HDPE geomembrane. Physically separated from acid storage — independent containment, independent drain and pump-out infrastructure. A shared containment that holds both ATS and acidic product (sulfuric acid, hydrochloric acid, or acidic fertilizer solution) is a worker-fatality hazard in a co-mingled spill.

Fittings and piping: Polymer (HDPE/PVC/CPVC) or 316L stainless (limited service, acceptable for piping). EPDM gaskets preferred; Viton acceptable. No copper, brass, bronze, or galvanized-steel — the thiosulfate-copper reaction forms copper sulfide and is visible within days of wetted service contact.

Venting: Atmospheric vent per API 2000. Chemical vent scrubber (caustic-absorber) is specified only at commercial terminal scale where ATS is heat-trace-warmed for winter crystallization-recovery service. Farm-scale ambient-temperature operation requires no scrubber.

Freeze protection: ATS fertilizer-grade 12-0-0-26S solution crystallizes at 14°F. Farm-scale outdoor tanks in USDA Zones 4 and colder need heat-trace or indoor storage in winter; Zones 5–6 are marginal; Zones 7+ rarely need freeze protection. Partial crystallization is recoverable by gentle warming (not above 110°F!) and recirculation.

H₂S gas detection: Fixed H₂S monitors are not typically required at farm-scale ATS storage (no acid segregation failures expected at farm operations), but commercial terminals and blending facilities that handle ATS adjacent to acid inventory should specify fixed H₂S detection at 10 ppm alarm set-point. Portable 4-gas meters (O₂, LEL, CO, H₂S) are standard PPE at fertilizer terminal operations.

Ammonium Thiosulfate FAQs — Field-Tested Answers

Can I store ATS in the same tank I use for liquid urea or UAN?

Yes during service changeover — HDPE and XLPE handle ATS, UAN, and liquid urea equally well. Triple-rinse during changeover. Note that UAN contains AN (ammonium nitrate) and ATS is not CFATS-regulated — so CFATS registration status may change depending on which chemistry is held. Verify fittings are polymer or 316L stainless (any brass or copper hardware installed for water-service baseline must be removed before ATS service).

My ATS tank developed a black precipitate at the bottom — what's wrong?

Almost certainly copper-sulfide precipitate from an unnoticed brass or copper fitting in the wetted path. Remove the tank from service, inspect every fitting (valve body, bulkhead fitting, sight gauge, bulkhead nipple) for copper-alloy material, replace with polymer or 316L, and flush thoroughly before returning to service. The precipitate is a visible and diagnostic sign of copper-alloy contamination.

Can I tank-mix ATS with glyphosate or 2,4-D?

Generally yes — ATS is compatible with most glyphosate and amine-2,4-D formulations at spray-solution dilution. Read the herbicide label for specific compatibility. ATS can actually act as a mild herbicide safener in some sulfonylurea applications.

What happens if my ATS tank gets to 110°F in summer?

ATS begins slow decomposition above 95°F and accelerates rapidly above 120°F. At sustained 110°F bulk temperature over days to weeks, you will see (1) yellow-to-amber sulfur haze development in the solution, (2) occasional SO₂ odor at the vent, and (3) gradual sulfur deposit at the tank bottom. The fertilizer chemistry is slightly degraded (sulfur precipitates out of plant-available form). Cool the tank (shade the site, partial shelter, or transfer to cooler storage), and resume service — the product is still usable but may need agitation to re-suspend settled sulfur before application.

Can I put my ATS tank next to my sulfuric acid tank in the same containment?

Absolutely not. A co-mingled spill of ATS and sulfuric acid releases H₂S gas at lethal concentrations within the containment volume. Use independent containment sumps, independent spill-recovery piping, independent drain-pump infrastructure, and physical separation of at least 10 feet (OSHA good-practice) between acid and ATS tank pads. Post warning signage at both sites identifying the segregation requirement. This is the single most important ATS site-design rule and has been the root cause of multiple worker fatalities at fertilizer terminals.

Is ATS regulated under CFATS or PSM?

No — ATS is not a CFATS Chemical of Interest and is not listed in OSHA PSM Appendix A. Standard fertilizer-dealer business licensure and state nutrient-management regulations cover the compliance bases. H₂S release in an acid-contact scenario triggers CERCLA notification (H₂S has a 100 lb RQ) and OSHA injury-reporting if worker exposure occurs — but the upstream ATS product itself is unregulated.

Can I use ATS to neutralize chlorine in my waste water?

Yes — ATS is a fast-acting chlorine-neutralization agent at stoichiometric dosing (roughly 2.85 mg ATS per 1 mg Cl₂). Small-batch industrial wastewater and pool/spa dechlorination use ATS in place of sodium thiosulfate or sodium metabisulfite. Storage of 12-0-0-26S fertilizer-grade ATS in the same HDPE tank used for fertilizer service is acceptable — the product specification is identical.

Related Chemistries in the Agricultural Nitrogen Cluster

Related chemistries in the agricultural-nitrogen cluster (urea + ammonium + UAN + phosphate-nitrogen fertilizer):

• Ammonium Sulfate (AS) — Standard NH4-S fertilizer
• Ammonium Nitrate (AN) — Nitrate-N fertilizer
• Monoammonium Phosphate (MAP) — NH4 phosphate fertilizer

Related Hub Pillars

For broader chemistry context, see the OneSource Plastics high-traffic chemical-compatibility hub pillars:

• Sulfuric Acid (H₂SO₄)
• Sodium Hypochlorite (NaOCl / bleach)