Ammonium Carbonate
Properties
| State | Solid (white crystalline powder) |
| Color | White |
| Solubility | Soluble in water; decomposes in hot water |
| Melting Point | 58°C (decomposes completely) |
| Boiling Point | Not applicable (decomposes to gases) |
About Ammonium Carbonate
Ammonium carbonate is the original chemical leavening agent — a white crystalline salt that decomposes completely on warming into three gases (ammonia, CO2, and water vapor) and leaves no residue behind, unlike modern baking powders that always deposit a sodium salt in the finished product. The decomposition begins around 58 °C and runs cleanly to (NH4)2CO3 → 2 NH3 + CO2 + H2O. That stoichiometry is the entire selling point: three gas molecules per formula unit, no taste residue, and the ammonia escapes during oven baking provided the dough is thin enough that the gas can diffuse out. Thin, crisp baked goods like Scandinavian springerle, German Lebkuchen, Greek koulourakia, and certain cracker styles still call for it specifically because nothing else gives the same dry, light texture without the slight metallic note that bicarbonate-based leavenings can leave. The compound has a long medical and theatrical history: dissolved in dilute solution it's the active ingredient in classic 'smelling salts' (sal volatile), where the released ammonia triggers the inhalation reflex through trigeminal-nerve irritation; powdered crystals heated in a confined space release ammonia and CO2 and have been used as cheap stage smoke. The chemistry student's interest is mostly in the decomposition itself — the textbook example of a thermally unstable ammonium salt where both the ammonium cation and the carbonate anion are unstable in their parent molecular forms.
Where you'll encounter it
If you've eaten a Scandinavian flat cookie that crunches under bite weight without snapping cleanly, you've probably eaten one made with baker's ammonia rather than baking powder — the texture is different in a way professional bakers can recognize at a single bite. In a chemistry teaching lab, ammonium carbonate is the textbook demonstration of a triple-decomposition reaction: warm the solid in a watch glass on a hotplate and it disappears into three colorless gases over a few minutes, with the ammonia readily detectable by smell and the residue (none) verifiable by mass. In qualitative analysis, ammonium carbonate solution is the classic Group IV cation reagent — it precipitates Ba²⁺, Sr²⁺, and Ca²⁺ as carbonates while leaving Mg²⁺ in solution, allowing the four alkaline-earth cations to be separated.
Common Uses
- Leavening agent for thin, crisp cookies and crackers
- Smelling salts (sal volatile) for stimulating the inhalation reflex
- Group IV cation precipitating reagent in qualitative analysis
- Cough-syrup expectorant component in older formulations
- Mordant in some traditional textile dyeing recipes
Safety Information
Releases ammonia gas on warming or contact with acid — irritating to eyes and respiratory tract at the levels released during baking, more dangerous in a confined space. Harmful if swallowed in large quantities, but the doses used in food are well below any toxicity threshold. GHS H302 and H319. Use in a ventilated kitchen or fume hood when warming powdered solid.
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.