Boiling point liquid is the highest temperature (and pressure) it will actually boil at. See also Vapour pressure of water. The element with the lowest boiling point is helium. Both the boiling points of rhenium and tungsten exceed 5000 K at standard pressure; because it is difficult to measure extreme temperatures precisely without bias, both have been cited in the literature as having the higher boiling point. As can be seen from the above plot of the logarithm of the vapor pressure vs. the temperature for any given pure chemical compound, its normal boiling point can serve as an indication of that
Bioseparation of 1,3-propanediol and proteins. Of the three chemicals water has the lowest boiling point (see the water, 1,3-propanediol, and glycerol articles for boiling point information), so it is removed as distillate in the first column. The bottoms of the first column is then sent to a second column, where BioPDO is removed as distillate because of its lower boiling point. Both columns operate under low pressure (55 mm Hg in the first column; 20 mm Hg in the second column) to lower the boiling points of the distillate and bottoms streams, thereby using a lower pressure steam than that for atmospheric columns.