Fluoric acid or HFO 3 is a hypothetical oxyacid of fluorine , molecular mass 68 g/ mole, a gaseous substance that can dissolve silicon , and keep it suspended in the gaseous state. So, it dissolves glasses, crystals and several precious stones. It is heavier than atmospheric air, is not flammable, and is poisonous when inhaled. Its smell is penetrating and somewhat similar to that of hydrochloric acid .

It corrodes animal and vegetable materials and light has no effect on it. It emits white fumes in the humid atmosphere. It is strongly acidic and therefore turns organic vegetables red. It precipitates calcium hydroxide and does not react with platinum , gold , silver mercury, tin , lead , antimony , cobalt , nickel and bismuth , but reacts with iron , arsenic and manganese  . Fluoric acid can be prepared by reacting "sodium fluorate" with sulfuric acid and cannot be stored in glassware. 2 NaFO 3 + H 2 SO 4 → Na 2 SO 4 + 2 HFO 3

References :https://books.google.com.br/books?id=uWNZAAAAIAAJ&pg=PA327&dq=%22fluoric+acid%22&hl=en&sa=X&ei=PdyJVaXjMYXZ-QHnsY3gBg&ved=0CDYQ6AEwBA#v=onepage&q=%22fluoric%20acid%22&f=false