Hydrazine hydrate is a small molecule with an outsized regulatory footprint. The technical content is straightforward – it is a strong reducing agent and a convenient nitrogen source – but almost every commercial decision around it depends on one question: what concentration of hydrazine, as distinct from hydrazine hydrate, is in the drum. This guide covers the properties, the concentration arithmetic that drives classification, the main applications, and the handling requirements. The specification is on the hydrazine hydrate 55% product page.
Identity and properties
| Property | Value | Practical significance |
|---|---|---|
| Formula | N2H4.H2O (hydrazine monohydrate) | The hydrate is not a solution of hydrazine in water – it is a defined compound that itself contains about 36% water by mass |
| CAS | 10217-52-4 (also registered as 7803-57-8) | Two registration numbers circulate for the same material; check which one your market’s registration uses |
| Molecular weight | 50.06 (hydrate); hydrazine itself is 32.05 | The ratio 32.05 / 50.06 is the conversion factor between hydrate and hydrazine content |
| Appearance | Clear, colourless liquid | Yellowing indicates iron contamination or decomposition |
| Odour | Ammonia-like | Detectable well below hazardous concentrations, which is useful as a warning but not as protection |
| pH | Weakly basic | Corrosive to some metals; reacts with acids |
| Reactivity | Strong reducing agent; reacts with oxidisers, acids, metal ions | Drives both its applications and its storage constraints |
The concentration arithmetic that decides everything
This is the single most important section for anyone buying or shipping hydrazine hydrate. Concentrations are quoted on different bases, and the difference is large.
| Basis | What it means | Example: a 55% hydrate grade |
|---|---|---|
| Hydrazine hydrate content (N2H4.H2O) | Mass fraction of the hydrate compound | 55% |
| Hydrazine content (N2H4) | Mass fraction of anhydrous hydrazine | Approximately 35% – because hydrazine is only about 64% of the hydrate by mass |
| Which one regulations use | Most transport classifications, hazard thresholds and export controls are written on the hydrazine figure | A “55%” product sits well below a 64%-hydrazine threshold, but the classification must be checked against the actual basis |
| Common confusion | Reality |
|---|---|
| “55% hydrazine” | A 55% hydrate solution is about 35% hydrazine. If a customer needs 55% hydrazine, they need roughly 86% hydrate |
| “100% hydrazine hydrate” | That is the pure hydrate compound – still only about 64% hydrazine |
| “Anhydrous hydrazine” | A different product entirely (CAS 302-01-2), far more hazardous and much more tightly controlled |
Practical consequence: never accept a concentration figure without its basis. A supplier quoting “55%” and a regulation quoting “64%” may or may not be talking about the same thing, and the difference decides whether a shipment needs an export licence.
How it is made
| Route | Chemistry | Notes |
|---|---|---|
| Urea process | Urea oxidised with hypochlorite in alkaline conditions | Widely used in China; generates sodium chloride and carbonate by-products that must be separated |
| Raschig process | Ammonia chlorinated to chloramine, then reacted with further ammonia | Classic route; large salt burden and steam consumption |
| Ketazine process | Ammonia, hydrogen peroxide and a ketone form a ketazine, which is hydrolysed to hydrazine with the ketone recycled | Lower salt load; the ketone recycle is the key to economics |
| Hydrogen peroxide direct routes | Ammonia plus hydrogen peroxide over a catalyst | Cleaner on paper; catalyst and selectivity are the commercial issues |
The production route matters to a buyer because it shapes the impurity profile – chloride from hypochlorite-based routes, sulphate and metals from catalyst systems – which is precisely what the specification limits address.
Reading the specification
| Parameter | Limit | What it is controlling |
|---|---|---|
| N2H4.H2O content | 55% min | The active figure; confirm the basis as above |
| Non-volatile content | 0.01% max | Inorganic residue; matters for boiler use and for any application where solids are unacceptable |
| Iron | 0.0005% max | The most important impurity. Iron catalyses hydrazine decomposition: a high-iron lot loses assay in storage and can evolve gas in a sealed drum |
| Heavy metals (as Pb) | 0.0005% max | Pharmaceutical and electronic purity gate |
| Chloride | 0.003% max | Corrosion of stainless steel in hydrazine systems, and catalyst poisoning |
| Sulphate | 0.0005% max | Purity indicator, particularly for reagent use |
Applications
| Application | Role | What the buyer should specify |
|---|---|---|
| Blowing agent manufacture | Raw material for azodicarbonamide (ADC), the main chemical blowing agent for plastics and rubber | Assay consistency and low metals; the reaction is sensitive to impurities |
| Boiler water treatment | Oxygen scavenger: N2H4 + O2 gives N2 and water, leaving no dissolved solids, and it passivates steel by converting haematite to magnetite | Low chloride and low iron are essential – the product is protecting the steel it travels through |
| Agrochemical synthesis | Nitrogen source in triazole, pyrazole and related heterocyclic routes | Consistent assay and controlled metal content |
| Pharmaceutical intermediates | Reducing agent and nitrogen source | Heavy metals and residual impurities with documentation |
| Chemical reduction | Reduction of metals, chromate and other oxidised species | Technical grade usually sufficient |
| Polymerisation | Component in some controlled radical and emulsion systems | Iron and oxygen content matter |
Boiler water treatment, in more detail
| Point | Detail |
|---|---|
| Reaction | Hydrazine reacts with dissolved oxygen to give nitrogen and water – no dissolved solids added to the boiler water, which is its main advantage over sulphite |
| Stoichiometry | Roughly 1 mg/L of hydrazine per 1 mg/L of dissolved oxygen in theory; practical dosing is a multiple of that, with residual hydrazine maintained at a target level |
| Kinetics | The reaction is slow at ambient temperature and fast above about 120 deg C, which is why hydrazine is used in the feedwater or directly in the boiler rather than in cold water |
| Passivation | Beyond scavenging, hydrazine converts iron oxide to a protective magnetite layer, which is why it is valued beyond simple deoxygenation |
| Residual monitoring | Hydrazine residual is measured colorimetrically and controlled to a target range – too little and oxygen passes, too much and the excess leaves the plant as a toxicant |
| Alternatives | Because of hydrazine’s toxicity classification, many plants have moved to carbohydrazide, DEHA or erythorbate, which are less hazardous and still effective |
Regulatory and export position
Hydrazine is toxic by inhalation, ingestion and skin contact, is a suspected carcinogen, and hydrazine-bearing products are controlled as an explosive precursor in some jurisdictions above defined concentration thresholds. Lower-concentration solutions can generally be exported with the correct documentation, but whether a specific grade requires a licence depends on the hydrazine concentration of the product and on the destination country – not on the hydrate figure alone.
| Item | What applies | What the buyer must do |
|---|---|---|
| Classification | Toxic, corrosive, suspected carcinogen; specific hazard statements depend on concentration | Confirm the classification used in your market, and that your storage and handling meet it |
| Export control | Some markets list hydrazine and its hydrate as an explosive precursor above a concentration threshold | Establish whether your grade and destination are in scope; apply for the licence if required |
| End-use declaration | Commonly required for controlled chemicals | State the application and commit to no re-export or diversion |
| Import registration | Registration is the buyer’s responsibility in most markets | Confirm your own registration covers this use before ordering |
| Transport | Classified by concentration; packing and labelling follow | Confirm with your forwarder, and note that a lower-concentration product may fall outside the most restrictive class |
| Documentation we provide | COA, SDS in the required language, and the supporting statements available for the grade | Tell us the destination and end use at enquiry so the correct documents are prepared |
Handling and storage
| Point | Requirement |
|---|---|
| Materials of construction | Stainless steel or polyethylene. Copper, brass and many alloys catalyse decomposition and must be avoided |
| Contamination control | Keep away from oxidisers, acids, rust and metal salts. Iron contamination causes gas evolution and assay loss |
| Ventilation | Local exhaust at decanting points; hydrazine vapour is hazardous |
| PPE | Full chemical protection including impervious gloves – hydrazine is absorbed through the skin |
| Storage | Sealed, cool, shaded, vented where required. Prolonged storage is inadvisable; order to consumption rate |
| First aid | Flush immediately with plenty of water; seek medical attention – skin absorption is a real pathway |
Buying notes
| Item | What to fix in writing |
|---|---|
| Concentration and basis | Hydrate content stated, and the corresponding hydrazine content – both, not one |
| Iron and chloride | The two impurities that decide whether the lot survives storage and protects the plant |
| Destination and end use | Declared at enquiry, because they determine the documentation and the licence question |
| Packaging | PE drums or IBC, with closures suitable for the material |
| Remaining shelf life | Agreed on delivery; hydrazine assays decline over time even in good storage |
| Documentation | Batch COA, SDS, and the export/import statements your destination requires |
Frequently asked questions
Is 55% hydrazine hydrate the same as 55% hydrazine?
No. A 55% hydrate solution contains about 35% hydrazine. The hydrate molecule itself is only about 64% hydrazine by mass, so the hydrate figure is always higher than the hydrazine figure for the same liquid.
Why is iron limited so tightly?
Because iron catalyses the decomposition of hydrazine. A contaminated lot will lose assay in storage and can generate gas in a sealed container – a genuine safety issue, not just a quality one.
Can hydrazine hydrate be shipped in lower concentrations?
Lower-concentration solutions are generally easier to export than high-concentration or anhydrous material, but the position depends on the destination and on the hydrazine concentration of the product. Confirm before quoting, and declare the end use so the documentation can be prepared.
Why do some plants no longer use hydrazine for boiler treatment?
Because of its toxicity classification. Carbohydrazide, DEHA and erythorbate have replaced it in many plants, at a higher chemical cost but with a much lower hazard profile.
How should hydrazine hydrate be stored?
Sealed, cool, shaded and in compatible materials – stainless steel or polyethylene, never copper alloys. Do not hold large stocks for long periods, and re-test the assay if a drum has been open or stored warm.