The latent heat of vaporization of mercury was found by Marignac to be 103 to 106.
The vaporization of a substance below its normal boiling-point can also be effected by blowing in steam or some other vapour; this operation is termed "distillation with steam."
A liquid boils when its vapor pressure equals the superincumbent pressure; consequently any process which diminishes the external pressure must also lower the boiling-point.
Thus the heat of fusion of ice (for H 2 O=18 g) is 1440 cal., and the heat of vaporization of water at 100°, for the same quantity, 9670 cal.
An objectionable feature of the system of allowing the vapour to escape from the still to the condenser through a loaded valve, viz: the irregularity of the distillation, is thus removed, and the benefits of regular vaporization and condensation under high pressure are obtained.