Cyanamide is sold in two forms that are chemically identical and commercially opposite: a 50% SL solution (CAS 420-04-2 in water, acid-stabilised) and a 95% crystalline solid. Buyers regularly compare them on price per tonne of product, which is the wrong comparison, and then discover the real differences in the warehouse rather than in the quotation. This article sets out the selection logic.
What Actually Differs
| Property | 50% SL | 95% crystalline |
|---|---|---|
| Physical form | Clear liquid, colourless to light yellow | Crystalline solid, melting at 45 – 46 °C |
| Cyanamide content | 50.0% min | 95% grade (specification issued against enquiry) |
| Water | About half the product | Low – and that is the problem as well as the benefit |
| Stabilisation | Acid buffer built in, pH 3.8 – 5.4 | Stability depends on keeping the solid cool and dry; no aqueous buffer |
| Dicyandiamide limit | 2.0% max | Specified per enquiry; the same chemistry applies |
| Handling | Pump, meter, dilute | Melt, dissolve, or dose as solid – all with heat or dust exposure |
| Freight per tonne of active | Twice the mass, half of it water | About half the mass for the same active |
| Practical shelf life | Months in a cool store | Shorter at ambient temperature; must be kept cool |
Note the shape of the trade-off: the water in the 50% SL is not just dead freight, it is also what keeps the product stable. Dimerisation to dicyandiamide is accelerated by concentration, by heat and by alkaline pH – and the crystalline form is concentrated, usually warm (it melts at 45 °C) and unbuffered. The solution is the forgiving form; the crystal is the effective form.
The Only Honest Price Comparison
| Basis | 50% SL | 95% crystalline |
|---|---|---|
| Product needed for 500 kg cyanamide | 1,000 kg | 526 kg |
| Freight mass advantage of the crystal | – | 47% less mass moved |
| Cost per kg of cyanamide | price per tonne / 0.50 | price per tonne / 0.95 |
| Handling cost to add | Pump and tank; no heat | Melting or dissolving energy, dust control, corrosion-resistant melter |
| Loss to dimerisation in store | Low if cool and acidic | Higher per month unless kept cool and dry |
A 95% crystal has to be priced below roughly 1.9 times the cost of the solution per tonne before it wins on delivered cost of active – and that is before the melting equipment, the heat and the shorter shelf life are counted. In practice the crystal wins for formulators who need high active concentration or a water-free reaction system, and the solution wins almost everywhere else.
Stability: The Same Reaction, Different Speeds
Both forms dimerise by the same route: two cyanamide molecules give one dicyandiamide molecule of the same total mass (2 x 42.04 = 84.08 g/mol). What differs is the rate, and the rate is driven by three variables:
| Variable | Effect | Implication |
|---|---|---|
| Temperature | Rate rises steeply with temperature | A hot warehouse ages the product faster than a long sea voyage in a cool container |
| pH | Base-catalysed; slowest in the 3.8 – 5.4 window | The solution is buffered; a melted crystal is not, and any alkaline contamination accelerates loss |
| Concentration | Higher concentration, faster dimerisation | The 95% solid is at the wrong end of this curve by definition – hence cold storage |
Two practical rules follow. First, never warm a cyanamide drum with an open flame or a high-wattage band heater: local overheating is exactly the condition that destroys the product. Second, if you melt the crystal, use it promptly and do not hold it molten – a molten heel left overnight is a batch of dicyandiamide in the making.
Dosing: Volume Versus Mass
This is where the solution form earns its keep in a plant. With a density of 1.065 – 1.095 g/mL, the 50% SL contains 532 – 548 g of cyanamide per litre, or 12.7 – 13.0 mol/L. Volume dosing therefore needs only a density check on the batch, and the arithmetic is a single multiplication. The solid form needs weighing, melting and – if it is to be metered – a heated, corrosion-resistant line with a known hold-up volume.
If you are validating a batch record, the cross-check is simple: litres x density x 0.50 = kg of cyanamide. A result more than a few percent off the COA assay means either the density or the assay is wrong.
Dilution Stability and Tank Behaviour
The 200-fold dilution test on the 50% SL specification confirms that the stabiliser holds at 0.25% cyanamide – the concentration a spray tank or a dilute reaction sees. A crystalline grade dissolved on site has no such guarantee: once you dissolve 95% material in your own water, you become the formulator and you must set your own pH and hold time. If your process runs dilute cyanamide for hours, the pre-stabilised solution is worth a premium.
Hazard Differences
Both forms carry the same toxicology – toxic if swallowed, harmful on skin, serious eye damage, skin sensitisation, and an alcohol-sensitising effect – but the exposure routes differ:
- Solution: splash and mist. Eye protection and gloves; bunded storage; no open pouring from height.
- Crystal: dust and hot liquid. Melting creates both a vapour/dust hazard and a burn hazard, and the solid is hygroscopic, so spilled material turns into a corrosive puddle.
Neither form may be repacked into unlabelled or food-grade containers, and both require the no-alcohol rule during handling.
Selection Table
| If your situation is… | Choose | Why |
|---|---|---|
| Agricultural dormancy breaking in the field | 50% SL | Traded standard, stabilised, easy to dilute |
| Dilute aqueous reaction run for hours | 50% SL | Buffered; no on-site formulation risk |
| Small plant, no melting equipment | 50% SL | Pump and meter; no heat, no dust |
| Water-free or high-concentration system | 95% crystalline | Minimum water and freight per unit active |
| Long sea freight to a hot climate | 50% SL, cool container | Lower dimerisation rate in the diluted, buffered form |
| Continuous process with melting capability and fast consumption | 95% crystalline | Freight saving realises; shelf life is not tested |
Frequently Asked Questions
Can I make 50% SL from the 95% crystal myself?
Technically yes – dissolve and acidify to pH 3.8 – 5.4 – but you then own the stability of the solution, and you have added water you paid freight on. Compare the fully loaded cost, including the buffer and the QC, before assuming it is cheaper.
Which form has the longer shelf life?
Per month of storage the stabilised 50% solution is usually the more stable, because it is diluted and buffered. The crystal keeps longer only if it is genuinely kept cool and dry.
Why does the crystal melt at only 45 °C?
Because cyanamide is a small, highly polar molecule with a low melting point. That is convenient for melt dosing and inconvenient for storage in a warm climate – a warehouse at 40 °C is already close to the melting range.
Do you supply both forms?
Yes. The 50% SL is a standard product with a published specification; the 95% crystalline grade is supplied against enquiry, with the specification issued for the specific request.
References and Disclaimer
- PubChem CID 9864 – cyanamide formula (CH2N2, 42.04 g/mol) and computed properties.
- Melting point 45 – 46 °C: CRC Handbook of Chemistry and Physics, as indexed in the PubChem record.
- Concentration conversions use the 50% SL density window (1.065 – 1.095 g/mL) and the assay limits stated above.
Disclaimer: technical and commercial information for industrial buyers, not a specification or SDS. Agricultural use is governed by the registered label in the destination country.
PolyBlueChem supplies hydrogen cyanamide 50% SL (CAS 420-04-2) at 50.0% min with dicyandiamide 2.0% max, and can quote the 95% crystalline grade against enquiry. Tell us the application, the plant’s handling capability and the destination, and we will confirm which form and which documentation fits. Hydrogen cyanamide 50% SL product page.