What is the PEN for flourine?

In 1670 a recipe containing Bohemian emerald (now known as calcium fluoride, CaF2) was used to etch glass. It seems that George Gore made a little fluorine through an electrolytic process but his apparatus exploded when the fluorine produced reacted with hydrogen from the other electrode. The element finally was isolated in 1886 by Ferdinand Frederic Henri Moisson who used an apparatus constructed from platinum. His reward was the Nobel Prize for chemistry in 1906.

The energies of combustion in fluorine of α-white phosphorus and three modifications of red phosphorus-amorphous I, crystalline IV and crystalline V-were measured. With the adoption of α-white phosphorus as standard state, the standard enthalpy of formation of PF5 (g) at 25° was calculated to be - 380.8±0.3 kcal mole-1. The enthalpies of transition at 25° for the following processes are reported: P (α-white) →P (amorphous red I), ΔHt=-3.9±0.4 kcal g-atom-1; P (α-white) →P (red V), ΔHt=-3.9±1.5 kcal g-atom-1; P (red IV) →P (red V), ΔHt=-1.2±1.0 kcal g-atom-1. High-temperature thermodynamic functions for PF5 (g) are also reported.