Elemental mercury vapour in air: the origins and validation of the 'Dumarey equation' describing the mass concentration at saturation

The Dumarey equation has been the dominant relationship used to calculate the mass concentration of saturated elemental mercury vapour in air for the calibration of mercury vapour measurement equipment for over 25 years. However, the origin of the equation, and the validation data supporting its accuracy have never been published. This paper addresses that deficiency, compares the Dumarey equation with other data sets to which it has been wrongly attributed in the past, and describes why it remains superior to the use of mercury vapour pressure data in combination with the ideal gas law, for the purposes of calibrating mercury vapour measurement equipment.