Fluorine: Anhydrous Hydrogen Fluoride with Potassium Hydrogen Fluoride Electrolysed at -23 °C in a Platinum U-Tube (Moissan 1886)

How Moissan first set fluorine free in 1886. Dry liquid hydrogen fluoride will not carry a current, but with a little potassium hydrogen fluoride dissolved in it, it does. In a small iridium-platinum U-tube cooled to -23 °C, current from 20 Bunsen cells gives fluorine at the positive pole and hydrogen at the negative. Result: fluorine gas, about 1.5-2 litres an hour. Source: Moissan, as given in Thorpe, A Dictionary of Applied Chemistry vol. 2 (1912), pp. 584-585, Fig. 3 (shown above). Fluorine and hydrogen fluoride are among the deadliest substances handled in a laboratory.