Hydrogen fluoride, liquid purification

Fluorination of nitrophenyl esters was carried out in stainless steel and Hastelloy autoclaves. Sulfur tetrafluoride used in fluorination was treated with mercury (16) to remove bromine, a consistent contaminant of the commercially available gas. Purification was essential for high yields. The presence of sufficient anhydrous hydrogen fluoride to ensure the presence of a liquid phase also appears to be important in obtaining reasonably good yields. Fluorination experiments are summarized in Table VI. 

In 1886, Henri Moissan (Figure 6.2) attempted the electrolysis of pure liquid HF. Purification was accomplished by combining the vapour with KF to get potassium hydrogen fluoride, KHF2 ... 

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