Properties of Hydrogen Cyanide (HCN)
Hydrogen cyanide (HCN) is a highly toxic, colorless, and flammable liquid at room temperature. It is used in various industrial applications, including the production of synthetic materials and certain chemicals, but it requires careful handling and is regulated due to its extreme toxicity.
The following table provides a comprehensive list of hydrogen cyanide properties in both SI and US customary/Imperial units at normal temperature and pressure (NTP).
Click on the icon to switch between Metric and Imperial units.
| Physical Properties | Metric |
|---|---|
| Molar Mass | 27.025 g/mol |
| Density (liquid) | 687.6 kg/m3 |
| Dynamic Viscosity (25°C) | 2.9 µPa·s |
| Thermal Properties | Metric |
| Melting Point | -13.3 °C |
| Boiling Point | 25.6 °C |
| Thermal Conductivity (25°C) | 0.226 W/m·K |
| Specific Heat Capacity (Cp) | 1326 J/kg·K |
| Critical Constants | Metric |
| Critical Temperature (Tc) | 183.5 °C |
| Critical Pressure (Pc) | 5.39 MPa |
| Critical Density (ρc) | 195 kg/m3 |
| Hazardous Data | Metric |
| Autoignition Temperature | 540 °C |
| Lower Flammability Limit | 5.6% |
| Upper Flammability Limit | 40% |
| NFPA Rating (Health) | 4 |
| NFPA Rating (Fire) | 4 |
| NFPA Rating (Reactivity) | 1 |
Unless stated otherwise, all values are taken at room temperature (approximately 20°C or 68°F) and 1 atm pressure. (1 atm = 101,325 Pa)
Related Pages
References: 1) Cardarelli, François. Materials Handbook: A Concise Desktop Reference. Switzerland: Springer International Publishing, 2018. 2) CRC Handbook of Chemistry and Physics, 97th Edition. United Kingdom: CRC Press, 2016-2017. 3) Yaws, Carl L. The Yaws Handbook of Physical Properties for Hydrocarbons and Chemicals. Netherlands: Elsevier Science, 2015. 4) Fire Protection Guide to Hazardous Materials, 14th Edition. United States: National Fire Protection Association, 2010.