Preparation and properties of hydrogen halides

Apparatus can be constructed in lead, copper, silver, or platinum, or, for more than 58 % HF, from steel paraffin-coated glass, polyethylene, celluloid, polychlorotrifluoroethylene, and polytetrafluoroethylene (Teflon) can also be used for reaction vessels. Glass dissolves rapidly in aqueous HF. 

Hydrogen fluoride and water form an azeotropic mixture, b.p. 1127750 mm, containing 38.26% of HF for boiling points of aqueous hydrofluoric acids see Ullmann s Encyclopaedia.1400 Almost anhydrous acid can be obtained from 48% acid by two distillations and from 70% acid by a single distillation. In the laboratory these distillations are best carried out in silver or platinum apparatus. 

5% HF is commercially available in steel bottles, those containing 10-20 kg being most suitable for laboratory purposes. 

Goggles, rubber gloves, and rubber aprons should be worn when working with HF Skin damaged by HF or fluoride should be washed at once in 10% ammonium carbonate solution. A slurry of MgO in a little glycerol is also recommended for HF bums. 

Fluorinated hydrocarbons of fatty consistency can be used for lubricating metal surfaces and taps, with an external seal of piceine. Packing rings of lead, soft iron, or copper are used when connecting metal apparatus. Litharge in glycerol is a suitable cement. 

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