Hydrogen chloride, anhydrous manufacturing methods

Attempts to manufacture anhydrous mercury(II) fluoride by methods more conventional than the action of elemental fluorine upon mercury(II) chloride (vide supra) showed that aqueous reagents invariably yielded a dihydratc salt which could not be converted into anhydrous mer-cury(II) fluoride, because it always eliminated hydrogen fluoride in preference to water. In an effort to circumvent this, mercury(II) fluoride generated in situ has been used as the reagent for the substitution of one or several halogens by fluorine in various types of compounds (see Houben-Weyl, Vol. 5/3, p202 for pre-1959 reports). 

---