The inorganic fluorine industry

The reaction is straightforward, although heating is required because it is endothermic. CaF2(s) + H2S04(1) = 2HF(g) -h CaS04(s) (2.15) 

The product is either liquefied by refrigeration or dissolved in water to give hydrofluoric acid. Inevitable impurities in this process are calcium carbonate and silica from the raw materials. These also react  

Silicon tetrafluoride itself reacts with hydrofluoric acid to give fluorosilicic acid (H2Sip6). Since these impurities consume sulfuric and hydrofluoric acids it is essential to use fluorspar which is very pure. Incidentally, there are vast quantities of the by-product calcium sulfate stored in the old salt mines in Cheshire, and a fortune awaits anyone who can find a use for it  

Hydrofluoric acid has to be handled with great caution since it is extremely corrosive to skin, eyes, mucous membranes and the lungs. It causes deep-seated burns if spilt on the skin and even after treatment these are very slow to heal. 

Fluoropolymers are ubiquitous and have special properties. The best known is PTFE (polytetrafluoroethylene), which is widely used as a coating for non-stick cooking ware, under its trade names Teflon or Fluon. Gore-Tex is made from expanded PTFE, and is used in outdoor clothes as it allows the fabric to breathe, whilst still retaining excellent water repellency. Similar polymers are used to give water and stain resistance to textiles, for example, Scotchguard .  

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As shown in Table 1.1, the number of chemicals manufactured as bulk commodities is large. Consequently, in this account we have focused on just a few representative examples that embody the major considerations which underpin the operation of a viable manufacturing unit. These are sulfuric acid phosphoric acid ammonia, nitric acid and nitrates the chlor-alkali industry and the inorganic fluorine industry. 

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