Hydrogen chloride (HCl)
Also called chlorohydric acid, hydrochloride, hydrochloric acid or hydrochloric acid gas, hydrogen chloride is an acid gaseous colourless, odourless but toxic.
HCl is very soluble in the water but it can also dissolve in certain other solvents such as methanol, protonate molecules or ions, and serve as an acid-catalyst for chemical reactions where anhydrous (water-free) conditions are desired.
Dissolution is accompanied by large heat.
Non flammable and thermically stable, HCl is nevertheless toxic and corrosive.
| Properties | ||
| Molecular formula Molar mass Exact mass Appearance Density Melting Point Boiling point Solubility in water Vapour Pressure Acidity (pKa) Basicity (pKb) | HCI 36.46 g mol-1 35.976677739 g mol-1 Colourless gas 1.490 g dm-3 -112 °C, 161 K, -170 °F -85 °C, 188 K, -121 °F 720 g L-1 (at 20 °C) 423 kPa (at 20°C) -7.0 21.0 | |
Where it comes from
The presence of HCl comes from waste and combustibles (e.g: PVC). It is also possible to find Chlorine in the form of inorganic salts (NaCl) in wood, paper and cardboard or in food and vegetable waste containing salt.
Impact on the people and the environment
In most industry sectors, the emission value limits defined by the European authorities are 10 mg/m3. Some of the effects of this acid gas on people are : lung irritation, suffocation, skin burns,dehydratation.
Environmental issues are mainly : acid rain, impact on plant growth and smog.