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Although hydrofluoric acid is regarded as a weak acid, it is very corrosive, even attacking glass when hydrated. [ 20 ] Dilute solutions are weakly acidic with an acid ionization constant K a = 6.6 × 10 −4 (or p K a = 3.18 ), [ 10 ] in contrast to corresponding solutions of the other hydrogen halides, which are strong acids ( p K a < 0 ).
Hydrofluoric acid [2] is most often used to etch glass in a special marker equipped with a tip formed by a bed with a round footprint that runs down a vertical surface. The flow intensity can be influenced by pressing the marker. After applying the liquid to the glass surface, a permanent impression is formed, which cannot be removed by cleaning.
Dealkalizing glass containers is accomplished by exposing the glass surface to reactive sulfur- or fluorine-containing compounds during the manufacturing process. A rapid ion-exchange reaction proceeds that depletes the inside surface of alkali, and is performed when the glass is at high temperature, usually on the order of 500–650 °C or ...
In 1771 Carl Wilhelm Scheele prepared the aqueous solution, hydrofluoric acid in large quantities, although hydrofluoric acid had been known in the glass industry before then. French chemist Edmond Frémy (1814–1894) is credited with discovering hydrogen fluoride (HF) while trying to isolate fluorine.
Limescale build-up inside a pipe reduces both liquid flow and thermal conduction from the pipe, so will reduce thermal efficiency when used as a heat exchanger.. A descaling agent or chemical descaler is a liquid chemical substance used to remove limescale from metal surfaces in contact with hot water, such as in boilers, water heaters, and kettles.
This mixture is a superacid stronger than pure sulfuric acid, by many orders of magnitude, according to its Hammett acidity function. It even protonates some hydrocarbons to afford pentacoordinate carbocations (carbonium ions). [1] Like its precursor hydrogen fluoride, it attacks glass, but can be stored in containers lined with PTFE ...
the sentance "Hydrofluoric acid is notoriously known to dissolve glass (SiO2):" is grossly misleading at best. silica does not simply = glass! Actually this statement is true, HF is used to etch glass. My A.P. chem teacher has a piece of glass that he etched his name into with HF.
Acid etching is done using hexafluorosilicic acid (H 2 SiF 6) which, when anhydrous, is colourless. The acid can be prepared by mixing quartz powder (silicon dioxide), calcium fluoride, and concentrated sulfuric acid ; the acid forms after the resulting mixture is heated and the fumes (silicon tetrafluoride) have been absorbed by concentrated ...