Hydrogen chloride

 

Hydrogen chloride

Chemical formula	HCl
OTP appearance	clear gas
Index of refraction	1.0004456
Molar Mass(g/mol)	36.46
Density(g/cc)	0.00149
Melting Point(°C)	-114.22
Boiling Point(°C)	-85.05
Solubility in water(g/L)	720
NFPA 704	0 3 1 ACID

Uses

Primary

• Key chemical intermediate for chlorine chemistry

Production

Extraction

Extracting hydrogen chloride from water (hydrochloric acid) is difficult due to an azeotrope at about 20% HCl. Adding 25% by weight calcium chloride (or similar amounts of magnesium chloride) to the hydrochloric acid. At a certain point, relatively pure, "dry" hydrogen chloride will evaporate from the mixture.

Synthesis

via sulfuric acid

• Combine sodium chloride and sulfuric acid

  NaCl + H₂SO₄ → HCl + NaHSO₄

via phosphoric acid

Since phosphoric acid is available "early", this is an excellent path.

• Combine sodium chloride and phosphoric acid

  3 NaCl + H₃PO₄ → 3 HCl(g) + Na₃PO₄ // can partially react to NaH2PO4 or Na2HPO4