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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Physical & Chemical properties

Appearance / physical state / colour

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Administrative data

Link to relevant study record(s)

Description of key information

7647 -01 -0, HCl,
This CAS number of this inorganic substance is both for the gas and the aqueous solution of the gas. The gas is colourless to slightly yellow and the concentrated solution in water is colourless and fuming. Both have a pungent irritating odour.
This substance is not produced nor transported as an aerosol nor as a gas under pressure.

Key value for chemical safety assessment

Physical state at 20°C and 1013 hPa:

Additional information

From: HSDB

CASRN: 7647-01-0

hydrogen chloride,the gas, and HCl, the aqueous acid (hydrochloric acid),have the same CAS Registry number. Since the gas becomes the acid in aqueous systems and volatilization of the gas can occur from aqueous systems, it is often difficult to determine which is being considered in a specific item in the literature.

See: 7647-01-0,Freezing point,waiver,O'Niel, 2001,rs

Sittig's Handbook of Toxic and Hazardous Chemicals and Carcinogens (5th Edition)

Description:Hydrogen chloride is a colorless to slightly

yellow gas or fuming liquid with a pungent, irritating

odor. May be shipped and stored as a cryogenic liquid.

The aqueous solution is known as hydrochloric acid or

muriatic acid and may contain as much as 38% HCl.

7647-01-0,Appearance/physical state/colour,Bell,2007,PHYSICAL AND CHEMICAL PROPERTIES OF CONCENTRATED HCL,rs

Clear, colourless, uniform Clear, colourless, uniform liquid.