# Commission Regulation (EC) No 761/2009 of 23 July 2009 amending, for the purpose of its adaptation to technical progress, Regulation (EC) No 440/2008 laying down test methods pursuant to Regulation (EC) No 1907/2006 of the European Parliament and of the Council on the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) (Text with EEA relevance), Division 1.3: PRINCIPLE OF THE TEST

Extent: E+W+S+N.I.

In general, the vapour pressure is determined at various temperatures. In a limited temperature range, the logarithm of the vapour pressure of a pure substance is a linear function of the inverse of the thermodynamic temperature according to the simplified Clapeyron-Clausius equation:
log p = Δ Hv 2,3 RT + constant
where:
p the vapour pressure in pascals
ΔHv the heat of vaporisation in J mol–1
R the universal gas constant, 8,314 J mol–1 K–1
T the temperature in K

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Source: https://www.legislation.gov.uk/eur/2009/761/annex/I/division/1/division/1.3 (the official version)
Page: https://openlegislation.uk/eu-regulation-2009-761/annex-I/division-1/division-1.3
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.