Properties

General
Name	Hydrogen iodide
Chemical formula	HI
Appearance	Colourless gas
Physical
Formula weight	127.91 amu
Melting point	222.4 K (-50.8 °C
Boiling point	237.77 K (-35.38 °C)
Density	1.7 ×103 kg/m3 (liquid)
Solubility	42.5 g in 100g water
Thermochemistry
ΔfH0gas	? kJ/mol
ΔfH0liquid	? kJ/mol
ΔfH0solid	? kJ/mol
S0gas, 1 bar	? J/mol·K
S0liquid, 1 bar	? J/mol·K
S0solid	? J/mol·K
Safety
Ingestion	Toxic, can be fatal.
Inhalation	Fumes may be fatal. Do not give unprotected mouth-to-mouth resuscitation.
Skin	May cause severe burns.
Eyes	Extremely dangerous.
SI units were used where possible. Unless otherwise stated, standard conditions were used. Disclaimer and references

The chemical compound hydroiodic acid is a highly acidic aqueous solution of hydrogen iodide (HI). It is highly corrosive and should be handled only with appropriate precautions. Hydroiodic acid is a commonly used chemical reagent and is one of the strong acids that ionize completely in aqueous solution. Concentrated hydroiodic acid has a pH of less than 1.