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.