Hydrogen Cyanamide at a Glance
Hydrogen cyanamide (H2NCN, CAS 420-04-2, MW 42.04) is the simplest member of the nitrile family that still carries a reactive, electrophilic carbon. It is a colourless crystalline solid when pure – melting at 45 – 46 °C – but almost all of it is traded and used as an aqueous solution, because the solid is hygroscopic, thermally fragile and awkward to dose. The commercial standard is 50% SL: a soluble-liquid formulation containing 50.0% minimum cyanamide, stabilised at pH 3.8 – 5.4, with dicyandiamide held below 2.0%.
Two facts explain the product’s commercial position. First, 66.6% of the molecule is nitrogen – two nitrogens in 42 g/mol – which makes it the cheapest nitrogen-dense building block for dicyandiamide, thiourea, guanidines and amidines. Second, the same molecule breaks bud dormancy in perennial crops, which is why a single industrial chemical appears in both a reactor and a vineyard spray programme. Those two uses run on different regulations, different customers and different value chains, and both are affected by the one property that governs handling: cyanamide dimerises to dicyandiamide unless it is kept cool and acidic.
Chemical and Physical Profile
| Property | Value | Note |
|---|---|---|
| CAS number | 420-04-2 | Also called cyanamide, carbamoylnitrile, aminocarbonitrile |
| Formula / MW | CH2N2 / 42.04 g/mol | PubChem CID 9864 |
| SMILES | N#CN | – |
| Nitrogen content | 66.6% (calculated) | 2 x 14.007 / 42.04 |
| Melting point | 45 – 46 °C | CRC Handbook value; the reason the solid is difficult to handle |
| Appearance | Colourless to light yellow clear liquid (50% SL) | Darkening indicates ageing |
| Water solubility | Fully miscible | Strongly hygroscopic in the solid form |
| Computed lipophilicity (XLogP) | -0.3 | PubChem computed value |
| Computed polar surface area | 49.8 Å2 | PubChem computed value |
| Stability in solution | Maximum at pH 3.8 – 5.4 | Dimerises to dicyandiamide outside this window |
| Reactivity | Electrophilic carbon; adds H2S, hydrazine, amines, alcohols | The basis of thiourea, aminoguanidine and guanidine chemistry |
The physical profile is unusual in one respect that matters commercially: a solution of cyanamide has a low vapour pressure and no flash point, so the 50% liquid is far easier to store and transport than the solid, even though the solid contains twice the active per tonne. That trade-off – freight versus shelf life – is the whole subject of grade selection and is covered separately.
How Hydrogen Cyanamide Is Made
Industrial cyanamide is not made from hydrogen cyanide. The dominant route starts from calcium cyanamide (CaCN2, "lime nitrogen"), which is produced by heating calcium carbide in nitrogen at high temperature:
CaC2 + N2 → CaCN2 + C
The calcium cyanamide is then hydrolysed and neutralised to liberate free cyanamide, which is separated from the calcium salt and stabilised:
CaCN2 + H2SO4 → H2NCN + CaSO4
| Input / output (per tonne of H2NCN) | Mass | Basis |
|---|---|---|
| Calcium cyanamide required | 1.90 t | 80.10 / 42.04 |
| Calcium sulphate co-product | 3.24 t | 136.14 / 42.04 (anhydrous basis) |
| Sulphuric acid consumed | 2.33 t | 98.08 / 42.04 |
Those stoichiometric ratios explain the structure of the industry better than any market report: cyanamide production is a co-product business. Every tonne of cyanamide brings 3.2 tonnes of gypsum with it, so producers are either integrated into calcium carbide and nitrogen, or they are buying mother liquor from someone who is. Carbon dioxide neutralisation (giving calcium carbonate instead of sulphate) is used where the downstream chemistry cannot tolerate sulphate.
The second half of the process is stabilisation, and it is where the specification comes from:
- Acidification to pH 3.8 – 5.4. Dimerisation to dicyandiamide is base-catalysed and slow in acid. The pH window on the COA is the visible result of this control step.
- Concentration to 50%. Higher concentrations are achievable but shorten shelf life, because dimerisation rate rises steeply with both concentration and temperature. This is why 50% – not 60% or 70% – became the traded standard, and why the 95% material is a solid that is kept cold.
- Buffer and stabiliser package. Phosphate or sulphate buffers hold the pH window through dilution on site, which is what the "dilution stability, 200 times" test on the specification actually measures.
Specification of the 50% SL Grade
| Property | Specification | What it controls |
|---|---|---|
| Appearance | Colourless or light yellow clear liquid | Ageing; haze means dimerisation or contamination |
| Cyanamide content | 50.0% min | Active content – the only figure you are really buying |
| Dicyandiamide | 2.0% max | Dimer already formed; a direct measure of loss |
| pH | 3.8 – 5.4 | Stabiliser integrity; prevents further dimerisation |
| Dilution stability (200x) | Stable | Performance at 0.25% use dilution |
| Density (20 °C) | 1.065 – 1.095 g/mL | Cross-check on assay; converts weight dosing to volume dosing |
The conversion that matters in the plant. 50% w/w at a density of 1.065 – 1.095 g/mL gives 532 – 548 g cyanamide per litre, equivalent to 12.7 – 13.0 mol/L. If you dose by flow meter rather than by weight, that is the number to put in the batch record. It also gives you a free sanity check: an apparent "50%" solution with a density of 1.04 is probably not 50%.
Application Overview
| Application | Role of cyanamide | Sector |
|---|---|---|
| Bud dormancy breaking | Plant growth regulator applied before bud break | Agriculture (grapes, kiwifruit, apples, blueberries, stone fruit) |
| Dicyandiamide manufacture | Dimerised under controlled conditions | Chemical intermediates, epoxy curing, fertiliser additives |
| Thiourea manufacture | Addition of H2S | Rubber chemicals, ore flotation, intermediates |
| Aminoguanidine / guanidines | Reaction with hydrazine or ammonium salts | Pharmaceutical and agrochemical intermediates |
| Nitrification inhibition | Active chemistry in cyanamide-based nitrogen fertilisers | Fertiliser |
| Guanylation and amidine synthesis | Electrophilic carbon attacked by N-nucleophiles | Fine chemicals, pharmaceuticals |
The Chemistry Buyers Care About: Dimerisation
Two cyanamide molecules combine to give dicyandiamide:
2 H2NCN → C2H4N4
The mass balance is exact – 2 x 42.04 = 84.08 g/mol – which makes the specification unusually easy to interpret: a 2.0% dicyandiamide figure means roughly 2.0% of the cyanamide charged has already dimerised. The reaction is accelerated by heat, by alkaline pH and by concentration. That single sentence explains three commercial facts:
- Why the product is acid-stabilised and why pH is on the specification rather than being a cosmetic line item.
- Why 50% and not 70% is the traded concentration – water dilutes the dimerisation rate.
- Why shelf life is measured in months, not years, and why hot warehouses are the single most expensive place to keep this product.
The practical consequence for users is that cyanamide is a rotation stock: use the oldest drum first, keep it out of sunlight and above 5 °C (do not freeze-thaw repeatedly), and re-test dicyandiamide if a drum has been open or stored through a summer.
Downstream Chemistry: What the Electrophilic Carbon Buys
| Reaction | Partner | Product | Industrial significance |
|---|---|---|---|
| Dimerisation | Cyanamide itself | Dicyandiamide (C2H4N4) | Latent epoxy curing agent; nitrification inhibitor |
| Addition | H2S | Thiourea (CH4N2S) | Ore flotation reagent, rubber accelerator intermediate, pharma |
| Addition | Hydrazine | Aminoguanidine (CH6N4) | Intermediate for heterocycles and pharmaceuticals |
| Addition | Ammonium salts / ammonia | Guanidine salts | Resins, pharmaceuticals, explosives precursors in some routes |
| Addition | Amines, alcohols, thiols | Substituted amidines / isoureas / isothioureas | Fine chemicals, agrochemical actives |
All of these share the same mechanism: the nitrile carbon is electrophilic and the two nitrogens make the resulting amidine or guanidine highly basic. That is why cyanamide chemistry runs in acid or buffered media and at controlled temperature – the same conditions that keep the starting material from dimerising.
Agricultural Use: Dormancy Breaking
In perennial fruit crops, cyanamide is applied to dormant wood to substitute for part of the chilling requirement, so that buds break earlier and more uniformly. Commercial dormancy-breaking formulations are typically around the 50% active level, which is one reason why 50% SL is the traded standard worldwide.
What a supplier can and cannot say about this use:
- Can: supply technical material to a stated assay, with documentation; describe the mode of action at the level of bud physiology; explain dilution, tank stability and compatibility considerations at the formulation level.
- Cannot: recommend a rate, a timing or a crop-specific programme. Those are set by the registered label in each country, and they differ.
- Must: make clear that registration is country-specific. Cyanamide is an approved plant protection active substance in some jurisdictions and restricted or unregistered in others; the buyer is responsible for confirming that the product may be imported, sold and used in the destination market.
Procurement and Dosing Arithmetic
| Question | How to answer it |
|---|---|
| Compare prices on what basis? | Per tonne of cyanamide, not per tonne of product: divide the price by the assay (0.50) before comparing with a 95% crystal. |
| How much active in a drum? | 200 kg of 50% SL = 100 kg cyanamide. At 12.7 – 13.0 mol/L, one litre contains about 0.53 – 0.55 kg. |
| What shelf life should I plan for? | Months, not years. Ask for the batch date and the dicyandiamide figure; a fresh batch should be well below the 2.0% limit, not at it. |
| Which pack? | 25 kg for trials, 200 kg drums for production, 1000 kg IBCs where the site can handle them – all HDPE, all with intact bungs. |
| What documents? | Per-batch COA, current SDS, and the registration or non-registration statement your market requires. |
Safety, Storage and Regulatory Position
- Toxicology: toxic if swallowed, harmful in contact with skin, causes serious eye damage, may cause an allergic skin reaction. Cyanamide is also an alcohol-sensitising substance – a disulfiram-like reaction follows alcohol exposure – so handling procedures must include a no-alcohol rule for the shift.
- Storage: 5 – 30 °C, out of sunlight, bungs tight, HDPE only. Do not store near alkalis or oxidising agents, and do not allow the product to dry out in open containers.
- Dilution: use clean water; do not adjust pH upward, because alkaline conditions accelerate dimerisation and reduce shelf life of the tank mix.
- Regulatory: cyanamide is an industrial chemical and, in agriculture, an active substance subject to plant-protection registration. It is not a narcotic, a drug substance or a controlled precursor. Export documentation, duties and any destination-specific registration requirement are confirmed per shipment.
Frequently Asked Questions
What is the difference between cyanamide and dicyandiamide?
Dicyandiamide (CAS 461-58-5) is the dimer of cyanamide: two molecules of H2NCN combine to give one C2H4N4. It forms spontaneously in cyanamide solution, which is why the 50% SL specification limits it to 2.0% max.
Why is 50% SL the standard concentration?
Because dimerisation rate depends on concentration and temperature. A 50% solution is a practical compromise between freight cost and shelf life, and commercial dormancy-breaking formulations use roughly the same active level.
Can cyanamide be used in organic farming?
That is a certification and registration question, not a supplier question, and the answer differs by scheme and country. Confirm with the certification body and the local registration authority.
Does the 50% solution freeze?
It can crystallise at low ambient temperature in cold climates. Thaw gently and mix before use; repeated freeze-thaw cycles are not good for the product. Do not apply heat directly to a drum.
What does the 200-fold dilution stability test mean?
It confirms that the stabiliser system still holds when the product is diluted 200 times – 0.25% cyanamide – with no haze, precipitation or gassing. It matters for spray-tank and dilute-reaction use where the product spends hours at low concentration.
References and Disclaimer
- PubChem CID 9864 – formula, molecular weight, SMILES and computed properties for cyanamide.
- Melting point 45 – 46 °C: CRC Handbook of Chemistry and Physics, as indexed in the PubChem record for cyanamide.
- Stoichiometric ratios (calcium cyanamide, sulphuric acid, gypsum) are calculated from the balanced equations above; industrial yields are lower and depend on the producer’s process.
- Assay-to-concentration conversions use the density window on the specification (1.065 – 1.095 g/mL at 20 °C).
Disclaimer: technical and commercial information for industrial buyers. It is not a specification, a safety data sheet, or an application recommendation for any crop. Agricultural use is governed by the registered label in the destination country, and handling must follow the supplier’s current SDS.
PolyBlueChem supplies hydrogen cyanamide 50% SL (CAS 420-04-2) at 50.0% min with dicyandiamide 2.0% max and pH 3.8 – 5.4, in 25 kg drums to 1000 kg IBCs, with per-batch COA and SDS. The 95% crystalline grade is available against enquiry. Tell us the application, the destination and the documentation you need, and we will confirm the grade and the commercial terms. View the hydrogen cyanamide 50% SL product page.