Ammonium Hydroxide 29%: The Complete Guide to NH₄OH Uses, Grades & Safety

Ammonium hydroxide (NH₄OH) is one of the most quietly important industrial chemicals in modern manufacturing. It cleans the silicon wafers in every smartphone you’ve ever owned. It darkens the cocoa in Dutch-process chocolate. It stabilizes natural rubber latex on its way from a Malaysian plantation to a hospital glove plant. It runs the buffer chemistry in thousands of analytical labs. And, in dilute form, it’s the active ingredient in your bottle of glass cleaner.

At 29%, ammonium hydroxide is the standard industrial concentration — strong enough to be useful in a single dose, dilute enough to handle (with proper PPE) without specialized cryogenic equipment. We supply 29% in both ACS Reagent Grade and Technical Grade, in pack sizes from 1-quart bottles to 275-gallon IBC totes. We field these specification questions every week from semiconductor procurement engineers, food formulators, contract cleaning manufacturers, and lab managers — so this guide bundles the answers in one place: what NH₄OH is, what it actually does, which grade you need, and how to specify it on a purchase order.

NH₄OH chemical name, formula and other names

NH₄OH is ammonium hydroxide, the name for ammonia dissolved in water. Its formula is written NH₄OH, NH₃·H₂O or NH₃(aq); all three describe the same solution, CAS 1336-21-6, with a molecular weight of 35.05 g/mol as NH₄OH (17.03 g/mol for the NH₃ it carries).

The NH₄OH formula is bookkeeping. It records the two ions ammonia forms with water, NH₄⁺ and OH⁻, but almost all of the dissolved ammonia stays as neutral NH₃ molecules, which is why chemists prefer NH₃(aq). PubChem's computed IUPAC name is azanium hydroxide; nobody orders it by that name.

What "29%" means: NH₃ basis vs NH₄OH basis

A 29% label means 29 g of NH₃ per 100 g of solution, about 15.3 mol/L at a specific gravity of 0.897. Some spec sheets state strength as NH₄OH instead. Because NH₄OH weighs 2.06 times as much as NH₃ (35.05 ÷ 17.03), 28–30% as NH₃ is the same liquid as roughly 58–62% "as NH₄OH". Check which basis a quote uses before you compare prices.

What is ammonium hydroxide? The chemistry under the label

Ammonium hydroxide is, strictly speaking, a misnomer. There is no stable molecule with the formula NH₄OH that you can isolate in a bottle. What’s actually in the bottle is an aqueous solution of ammonia gas (NH₃) dissolved in water (H₂O), with the two species existing in dynamic equilibrium:

NH₃ + H₂O ⇌ NH₄⁺ + OH⁻

The equilibrium sits far to the left. At room temperature, fewer than 1 in 200 dissolved ammonia molecules (about 0.4% in a 1 M solution, about 0.1% in 29% stock) has actually grabbed a proton from water to form the ammonium cation NH₄⁺ and a hydroxide anion OH⁻. The rest stays as free NH₃. So when a label reads "29% ammonium hydroxide," what’s really in the bottle is approximately 29% by weight ammonia in water — with a tiny fraction of that ammonia ionized at any given instant.

This single fact — that it’s mostly free ammonia, not ionized hydroxide — explains nearly every property of NH₄OH that surprises new users:

• It smells. Ammonia is so volatile (pure ammonia has a vapor pressure of about 8.5 atm, per the NIOSH Pocket Guide) that a 29% solution constantly gives off NH₃ gas, and even a sealed bottle leaks it through caps and gaskets.
• It loses strength over time. Open the bottle and ammonia escapes preferentially — the solution gets weaker every time you use it. A 29% bottle stored with a poor seal can drop to 26% in months.
• It freezes the wrong way. Concentrated solutions don’t freeze sharply; they slush. PubChem lists a freezing point of −58°C for a 25% solution, well below typical winter shipping conditions.
• It plays havoc with copper and brass. Free ammonia forms intensely colored, soluble copper-amine complexes — which is why you never store ammonium hydroxide in copper-fitted plumbing.

Key physical properties (29% solution at 25°C)

Strong base or weak base? The 29% question

Is NH₄OH an acid or a base?

NH₄OH is a base, and a weak one. Dissolved ammonia takes a proton from water (NH₃ + H₂O ⇌ NH₄⁺ + OH⁻) with K_b = 1.77 × 10⁻⁵ (pK_b 4.75) at 25°C, so it raises pH but ionizes only partly. Its conjugate acid, the ammonium ion NH₄⁺, has a pK_a of 9.25.

Each tenfold increase in ammonia raises the pH by only about half a unit. That flat curve is the signature of a weak base: a strong base such as sodium hydroxide would climb a full unit per tenfold step.

This question shows up constantly in chemistry classes and on procurement specs, and the answer is genuinely a little subtle. Ammonium hydroxide is a weak base by classical Brønsted-Lowry definition — but at 29% concentration, it has plenty of OH⁻ kinetics to act like a strong base in many practical applications.

Ammonia is a weak base because, as we saw above, well under 1% of dissolved NH₃ (about 0.1% in 29% stock) picks up a proton at any instant. The pK_b of 4.75 quantifies that weakness.

So why does 29% NH₄OH still feel "strong" in the lab?

• Concentration overcomes weakness. Even a small ionization fraction times a large total concentration produces meaningful OH⁻. A 29% solution has roughly 15 molar total ammonia. The ~0.1% ionized fraction still gives about 0.016 M OH⁻, a calculated pH near 12.2.
• The Le Chatelier reservoir. When you consume OH⁻ in a reaction, the equilibrium shifts right and replaces it. The 29% solution holds an enormous reservoir of free NH₃ waiting to ionize on demand. So while sodium hydroxide gives you all its base up front, ammonium hydroxide releases it kinetically as you use it — a different shape, but plenty of total capacity.
• Buffering at the bench. The same equilibrium that makes ammonia weak makes ammonium-ammonia mixtures excellent buffers around pH 9–10. This is why ammonia chemistry shows up in so many lab buffer recipes — it self-stabilizes against perturbation in a way strong bases cannot.

Is ammonium hydroxide the same as ammonia?

Not exactly. Ammonia (NH₃, CAS 7664-41-7) is a gas at room temperature; ammonium hydroxide (CAS 1336-21-6) is that gas dissolved in water. The solution constantly gives off ammonia vapor, so the two share a smell and the same airborne exposure limits, but they differ in physical state, strength, CAS number and DOT hazard class.

The practical difference: anhydrous ammonia needs pressure-rated tanks and fittings, while ammonium hydroxide ships in HDPE bottles, pails, drums and totes. When a procedure says "ammonia" for a bench or cleaning job, it almost always means the aqueous solution.

The 6 industries that run on 29% NH₄OH

Outside of the cleaning aisle, ammonium hydroxide is mostly invisible to the public — but it’s a foundation chemical in six major commercial sectors. Each uses 29% as the standard incoming concentration; each dilutes or reacts it differently downstream.

The cleaning chemistry: why ammonia outperforms detergent on glass

If you’ve ever wondered why your $4 bottle of glass cleaner doesn’t leave streaks while your soapy water does, the answer is volatility. Soap and detergent solutions leave a thin surfactant film as the water evaporates; that film is what catches sunlight and shows streaks. Ammonia, by contrast, evaporates entirely — along with the water that carried it — leaving nothing behind on the glass. The cleaning happens; the residue doesn’t.

What ammonia actually does on a dirty surface

Three mechanisms work in parallel. The high pH (~11) saponifies skin oils and ester-based residues, converting them to water-soluble salts. The free ammonia molecules act as a mild solvent for nicotine, smoke residue, and other amine-soluble grime. And the fast-evaporating water/ammonia carrier means nothing pools on a vertical surface long enough to drip-dry into streaks.

Concentration math for the formulator

Concentration guide: 10%, 19%, 28%, 29% — and why we stock 29%

Ammonium hydroxide is sold across a wide range of concentrations, and the right pick depends almost entirely on whether you’re buying for end-use or as a feedstock. Higher concentration costs less per pound of available ammonia, ships in fewer drums, and gives you formulation flexibility — at the cost of stricter handling rules. Lower concentration is simpler to use directly but cost-inefficient at any meaningful volume.

The available concentration grades

Why 29% is the sweet spot

29% sits at a deliberate engineering optimum. It’s strong enough that you’re not paying to ship water, but dilute enough that it’s stable at typical warehouse temperatures (vapor pressure rises sharply above 30%). It’s the standard concentration on every major chemical distributor catalog and the assumed input for every published industrial procedure — RCA SC-1, USP cocoa alkalization, FDA-direct-food-additive specs, MIL-A-43447 latex preservation. If a procedure says "ammonium hydroxide" without specifying concentration, it almost always means 29%.

For most operations, the math is straightforward: buy 29%, dilute on demand to your working strength. A 5-gallon pail of 29% NH₄OH yields ~50 gallons of 3% glass cleaner concentrate. The same 50 gallons bought as ready-to-use 3% costs roughly 4–5x more before freight is even calculated.

ACS Reagent vs Technical Grade: which do you actually need?

The 29% concentration tells you what fraction of the bottle is ammonia. The grade tells you how clean the rest is — specifically, what trace impurities are allowed and how rigorously they’re certified. We supply 29% in both ACS Reagent Grade and Technical Grade, and the right pick is rarely about purity sensitivity in the abstract; it’s about whether your downstream process is sensitive to trace metals.

When ACS Reagent is required

Use ACS Reagent Grade when trace metal contamination would interfere with the downstream chemistry: complexometric titrations, ion chromatography mobile phases, semiconductor wafer cleaning (trace Fe and Cu can deposit on wafer surfaces and ruin device performance), trace-metals analytical work, sensitive pharmaceutical synthesis, and any procedure where the published method specifies "ACS Reagent Grade" or "ASTM Type II" reagent. Spending the premium is cheap insurance against a contaminated batch wasting downstream work.

When Technical Grade is the right call

Use Technical Grade for industrial cleaning manufacture, agricultural ammonia injection, latex stabilization, large-volume neutralization (acid-stream pH adjustment in wastewater treatment), most food formulation (assuming you carry separate FCC documentation), and any process where the chemistry tolerates routine industrial-purity input. The Technical Grade COA still certifies assay — you know you’re getting 29% — it just doesn’t certify trace-metal limits. For a contract cleaner formulator making 10,000 gallons of glass cleaner, the trace-iron question is irrelevant; for an analytical chemist running EDTA titrations, it’s the entire ballgame.

Safety: TLV, PPE, storage, and the never-mix list

29% ammonium hydroxide is corrosive (DOT Class 8) and acutely toxic via inhalation. The hazard is dominated by the high vapor pressure of free NH₃: just opening a container in still air will produce immediately detectable concentrations near the cap. Standard industrial controls work, but only if applied. Operations that "just go quick" without ventilation are how chronic exposures — and ER visits — happen.

Is ammonium hydroxide safe for humans?

No. Concentrated ammonium hydroxide is corrosive: it carries GHS H314 (causes severe skin burns and eye damage), and its vapor can irritate the respiratory tract (H335). OSHA limits ammonia in workplace air to 50 ppm over 8 hours; NIOSH recommends 25 ppm, 35 ppm short-term, and sets 300 ppm as immediately dangerous to life or health.

Household ammonia runs 5–10%, and ATSDR records rare cases where swallowing it caused severe burns to the esophagus. FDA lists ammonium hydroxide as GRAS for specific food uses (21 CFR 184.1139); that listing does not apply to the ACS or Technical grades we sell. It is also classified H400, very toxic to aquatic life, so it does not go down a drain undiluted. Read the Safety Data Sheet before opening a container and follow its first-aid section if exposure happens.

Does NH₄OH have a smell?

Yes. Ammonium hydroxide has the sharp, pungent, suffocating smell of ammonia, because free NH₃ escapes from the solution all the time. ATSDR puts the odor threshold at 5 ppm, a tenth of the OSHA limit, so you smell it long before the legal limit. Ammonia also causes olfactory fatigue: during a long exposure the smell fades even when the concentration has not dropped, so do not use your nose as the gauge.

Exposure limits

• OSHA PEL: 50 ppm 8-hr TWA
• NIOSH REL: 25 ppm 8-hr TWA, 35 ppm 15-min STEL
• ACGIH TLV: 25 ppm 8-hr TWA, 35 ppm 15-min STEL
• NIOSH IDLH: 300 ppm
• Detection threshold: ~5 ppm — you can smell it well below the OSHA limit, which is the warning sign that ventilation isn’t adequate

Required PPE for handling 29%

• Chemical splash goggles (full ventilation goggles — not safety glasses)
• Face shield over goggles when decanting or pouring
• Nitrile or butyl rubber gloves (avoid latex — ammonia degrades natural rubber)
• Long-sleeve chemical-resistant apron or coverall
• Closed-toe chemical-resistant footwear
• Local exhaust ventilation (fume hood for small-scale; LEV snorkels or full slot ventilation for production)
• Cartridge respirator (ammonia-rated, e.g., NIOSH "K"-cartridge) for backup; full-face SCBA for spill response

Storage rules

• Cool (under 70°F where possible), well-ventilated, away from direct sunlight
• Original sealed container preferred; if decanting, use HDPE or stainless steel — never copper, brass, zinc, aluminum, or galvanized steel
• Segregate from acids, oxidizers, halogens, and hypochlorites
• Keep containers vented or use pressure-relief caps — sealed bottles in a warm warehouse can develop measurable internal pressure

Spill response and first aid

For small spills (under 1 gallon): evacuate the area, ventilate, and absorb with vermiculite or sand. Do not flush large volumes to drain without dilution — high-pH ammonia slugs damage biological wastewater treatment. For skin contact, flood with water for 15 minutes minimum and remove contaminated clothing. For eye contact, flush with eyewash for 15 minutes and seek medical evaluation immediately. For inhalation, evacuate to fresh air and seek medical evaluation if any respiratory irritation persists past a few minutes.

Does vinegar neutralize ammonia?

Yes, chemically. The acetic acid in vinegar reacts with ammonia to form ammonium acetate (NH₃ + CH₃COOH → CH₃COONH₄), a salt that does not evaporate, so the ammonia smell drops. That makes a vinegar rinse reasonable for a small spill of household-strength cleaner on a hard surface.

For 29% stock, follow the SDS spill procedure instead. Acid-base neutralization of a concentrate releases heat, and an open pool keeps giving off ammonia vapor while you work on it. Never use vinegar on skin or eyes. For skin or eye contact, follow the first-aid section of the SDS.

Buying smart: pack sizes, freight, and how we ship 29%

For most industrial buyers, the right pack size is determined by usage rate divided by shelf-life concerns. 29% NH₄OH stored properly has a 2–3 year shelf life, but every time a container is opened, ammonia escapes preferentially — so smaller containers used quickly are often more cost-effective than a large drum used over a year. We supply the full range:

What to specify on a purchase order

To avoid back-and-forth on a procurement spec, include all five of these fields:

1. Concentration: "29% NH₄OH" (or 28–30% range if your spec accepts it)
2. Grade: ACS Reagent or Technical (or FCC for food applications)
3. Pack size: By volume and container type (quart bottle, gallon bottle, 5-gal pail, 55-gal drum, 275-gal tote)
4. Documentation: COA on request, no charge. SDS is required for any hazmat order. TDS if your QA chain wants the full data sheet.
5. Freight method: Ground LTL is standard. Some destinations require dock height or liftgate specifications — confirm in advance.

Lead time and shipping windows

Most pack sizes ship within 1–2 business days from our Texas warehouse. IBC totes and full-pallet drum quantities sometimes require 3–5 business days for crating and freight scheduling. We ship 29% by ground only, no air freight, so transit is dictated by carrier transit map, typically 2–5 business days continental US. We process orders during business hours with email confirmation; we don’t make same-day shipping promises that ground LTL networks can’t deliver on.