ISO 3993:1984

Liquefied petroleum gas and light hydrocarbons — Determination of density or relative density — Pressure hydrometer method

The prescribed apparatus shall not be used for materials having gauge vapour pressures higher than 1,4 MPa (absolute vapour pressure 1,5 MPa) at the test temperature. Alternative calibration procedures are described, but only the one using a certified hydrometer is suitable for the determination of density to be used in calculations of qualities for custody transfer or fiscal purposes.