Fuming

Fuming is a phenomenon displayed by certain liquids and a few solids. It manifests in visible fumes, consisting of droplets of fog appearing when the liquid contacts air. Fumes are usually corrosive and/or toxic. Chemicals that readily hydrolyze in moist air will fume vigorously.

Specific fuming liquids and solids

Acids

• Fluorosulfuric acid fumes in moist air, releasing a mist of sulfuric acid and hydrofluoric acid.
• Hydrochloric acid fumes when in high concentrations; the fumes consist of the acid itself and are formed when hydrogen chloride gas that escapes the solution combines itself with water vapor found in air. The fumes have a characteristic smell of hydrogen chloride.
• Nitric acid fumes at high concentrations. The fumes have a characteristic smell of nitric acid.
• Sulfuric acid does not fume at room temperature, but is known to fume when hot. The fumes are a mixture of sulfuric acid droplets and sulfur oxides. The fumes do not have a strong smell but pose a potent choking hazard.
  • Oleum produces fumes similar to those of hot sulfuric acid, however, it fumes profusely even when cold.
• Trifluoroacetic acid will fume in open air, but it does not hydrolyze in presence of water.
• Aqua regia readily fumes, giving off nitrogen dioxide and nitrosyl chloride.

Amines

• Ethylenediamine readily fumes in moist air, forming a hydrated form, and sometimes even carbonate.
• Hydrazine fumes significantly in open air, forming hydrates and carbonates.

Elements

• Bromine is known to fume at standard conditions, which makes storage difficult.
• Iodine does not fume strongly at room temperature, though if let a small sample on a white surface, a yellow stain will rapidly form on the surface around the iodine. Iodine itself will slowly sublime, effect which grows stronger with temperature, visible fuming appearing at high temperatures.
• White phosphorus, while not a liquid, will readily oxidize in open air and give off phosphorus pentoxide fumes and may even catch fire.

Halides

• Acetyl chloride hydrolyzes in contact to atmospheric moisture, giving off hydrogen chloride and acetic acid.
• Chromyl chloride hydrolyzes releasing hydrogen chloride and hexavalent chromium
• Disulfur dichloride hydrolyzes when exposed to moist atmosphere, giving off hydrogen chloride and sulfur dioxide.
• Phosphorus pentabromide hydrolyzes rapidly when exposed to atmosphere, giving off hydrogen bromide fumes.
• Phosphorus pentachloride hydrolyzes rapidly when exposed to atmosphere, giving off hydrogen chloride fumes.
• Phosphorus tribromide hydrolyzes rapidly when exposed to atmosphere, giving off hydrogen bromide fumes.
• Phosphorus trichloride hydrolyzes rapidly when exposed to atmosphere, giving off hydrogen chloride fumes.
• Phosphorus triiodide hydrolyzes when exposed to moist atmosphere, giving off hydrogen iodide and iodine fumes.
• Phosphoryl bromide hydrolyzes rapidly when exposed to atmosphere, giving off hydrogen bromide fumes.
• Phosphoryl chloride hydrolyzes rapidly when exposed to atmosphere, giving off hydrogen chloride fumes.
• Sulfur dichloride hydrolyzes when exposed to moist atmosphere, giving off hydrogen chloride and sulfur dioxide.
• Sulfuryl chloride hydrolyzes when exposed to atmosphere, giving off hydrogen chloride and sulfur dioxide.
• Thionyl chloride hydrolyzes and fumes similar to sulfuryl chloride.
• Tin(IV) chloride hydrolyzes in moist air, releasing hydrogen chloride and tin(II) oxide.
• Titanium(IV) chloride readily fumes in moist air at any temperature, giving off hydrogen chloride and titanium dioxide mist.

Oxides

• Sulfur trioxide hydrolyzes strongly in open air, giving off copious amounts of sulfuric acid.

Safety and hazards

Working with fuming chemicals should be done outside or in a fumehood. Never work with them in a poorly ventilated room.

References

Relevant Sciencemadness threads

• HCl fuming