Ammonia
Properties
| State | Gas at room temperature (pungent odor) |
| Color | Colorless |
| Solubility | Highly soluble in water (31% by mass at 25°C) |
| Melting Point | -77.7°C |
| Boiling Point | -33.3°C |
About Ammonia
Ammonia is one of the most consequential industrial chemicals ever made — about 150 million tonnes are produced every year via the Haber–Bosch process, and the resulting fertilizer chain (ammonia → urea or ammonium nitrate → field application) supplies the nitrogen that feeds an estimated half of the human population. The catalytic synthesis itself is an extraordinary piece of chemistry: triple-bonded N2 is one of the most kinetically inert small molecules known, and Haber–Bosch breaks it open at 400–500 °C and 150–300 bar over an iron-based catalyst, then combines it with hydrogen (typically from steam reforming of methane) to give NH3. The thermodynamics favor product formation only at high pressure; the kinetics require high temperature; the engineering compromise that makes both work simultaneously is what won Haber and Bosch their Nobel prizes (1918 and 1931). The molecule itself is a useful textbook case for several core concepts: trigonal pyramidal geometry from one lone pair on nitrogen (compared to trigonal planar BH3, which has none), basic behavior in water (Kb ≈ 1.8 × 10⁻⁵, exactly matching acetic acid's Ka — a coincidence that students sometimes notice), and a strong inversion-tunneling effect on the umbrella mode that's been used as a frequency reference in atomic clocks.
Where you'll encounter it
If you've smelled industrial-strength glass cleaner, that pungent sharpness is dilute aqueous ammonia at a few percent — strong enough to cut grease and break up urine residues, dilute enough to handle without protective gear in a kitchen. In agriculture, anhydrous ammonia is the cheapest form of nitrogen fertilizer per kilogram of N delivered, applied directly to soil through ground-injection rigs that schedule winter or pre-plant applications across millions of acres in the U.S. corn belt. In chemistry, NH3 is a textbook weak base for general-chem buffer problems, the nitrogen source in Birch reduction (where it's condensed as a deep-blue liquid metal solution with sodium or lithium dissolved electrons), and the refrigerant in industrial chillers — its 1.4 MJ/kg latent heat of vaporization is hard to match with halocarbon refrigerants and it has zero ozone depletion and zero global warming potential.
Common Uses
- Haber–Bosch synthesis feedstock for urea and ammonium nitrate fertilizer
- Nitric acid synthesis via the Ostwald process
- Industrial refrigerant (zero-ODP, zero-GWP alternative to halocarbons)
- Birch-reduction solvent and nitrogen source for sodium-amide chemistry
- Glass-and-surface cleaner formulations as dilute aqueous ammonia
Safety Information
Toxic by inhalation — high concentrations produce immediate eye and airway burns, and exposures above ~300 ppm can be fatal. The odor is detectable around 5 ppm, well below dangerous concentrations, which is fortunate since ammonia provides its own warning before hazardous levels are reached. Anhydrous liquid ammonia is also a cryogenic burn hazard (boiling point -33 °C). Compressed cylinders require pressure-rated regulators and outdoor storage. GHS H221, H280, H314, H331.
This safety summary is for educational reference only and may not be complete. It is not a substitute for Safety Data Sheets (SDS), medical advice, or professional chemical safety guidance. Always consult appropriate SDS and qualified professionals before handling chemicals. We deliberately do not publish occupational exposure limits or other regulatory thresholds: those values are revised over time and differ between jurisdictions, so the only correct source is the current SDS and the regulations that apply where you work.