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Physical & Chemical properties

Vapour pressure

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Description of key information

Based on the data presented in discussion, the substance is fully gaseous at atmospheric pressure and 25°C. Thus, there can be no liquid/vapour equilibrium: vapour pressure does not apply.

Key value for chemical safety assessment

Additional information

The substance is fully gaseous at atmospheric pressure and 25°C because these conditions are well below the critical pressure (Pcr) and well above the critical temperatures (Tcr), of the three constituents making up for ~97% of its composition:

  • Carbon monoxide: Pcr 3.5 MPa and Tcr -140°C from two sources (Air Liquide. Gas Encyclopedia - CO. Available on-line at http://encyclopedia.airliquide.com/Encyclopedia.asp?GasID=45, consulted 05/20/2016) (O'Neil, M.J. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals. Whitehouse Station, NJ: Merck and Co., Inc., 2006., p. 294).
  • Hydrogen: Pcr 1.3 MPa and Tcr -240°C from two sources (Air Liquide. Gas Encyclopedia - H2. Available on-line at http://encyclopedia.airliquide.com/Encyclopedia.asp?GasID=36, consulted 05/20/2016) (Budavari, S. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals. Whitehouse Station, NJ: Merck and Co., Inc., 1996., p. 821).
  • Nitrogen: Pcr 3.4 MPa and Tcr -147°C from two sources (Air Liquide. Gas Encyclopedia - N2. Available on-line at http://encyclopedia.airliquide.com/Encyclopedia.asp?GasID=5, consulted 05/20/2016) (O'Neil, M.J. (ed.). The Merck Index - An Encyclopedia of Chemicals, Drugs, and Biologicals. Cambridge, UK: Royal Society of Chemistry, 2013., p. 1228).