Containers hydrogen fluoride

Anhydrous hydrogen fluoride and hydrofluoric acid react with substances containing silica and silicon oxide to form silicon tetrafluoridc and fluorosilic acid. SiF, a colorless gas at ambient temperature, is liighly toxic. An equilibrium mixture of SiF in the presence of moisture also contains hydrogen fluoride and hydrofluoric acid. 

The crude product contains hydrogen fluoride which is removed by the addition of boric acid to the wash water (H3BO3 -f-4HF — HBF4 + 3H2O). The sodium fluoride disposes of... 

As indicated above, the crude product contains hydrogen fluoride. The sodium fluoride disposes of this by-product by the reaction NaF + HF — NaHF. An alternative procedure is to pour the crude product into water and to separate the product by extraction with pentane. 

J. C. Hake, M. M. Rieger, G. M. Schmid, and P. A. Kohl, Electrochemical etching of silicon in non-aqueous electrolytes containing hydrogen fluoride or fluoroborate, J. Electrochem. Soc. 146, 1960, 1999. 

This property makes HF suitable for etching glass and is the reason that hydrogen fluoride must be kept in plastic or inert metal (for example, Pt) containers. Hydrogen fluoride is used in the manufacture of Freons (see Chapter 17) for example. 

Fig. 9.8. Schematic behaviour of the partial conductivities due to ion states and to orientational defects in an ice crystal containing hydrogen fluoride.

In late 2005, a refinery operator died as he prepared to purge a vessel. He connected a hose from a nitrogen utility station to a vessel that was still pressurized with a pressure higher than the hose rating. The hose burst and the refinery operator was sprayed by a stream of chemicals that contained hydrogen fluoride. This operator was not wearing the specified Class C protective clothing (PPE) for the task. His neoprene jacket was unzipped. He perished from the exposure [6]. 

The reactions produce either gypsum or anhydrite and a gas containing hydrogen fluoride (Sutter and Burt, 2001). 

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