Hydrofluoric acid, etching glass with

Hydrofluoric acid is the most basic common precursor of most fluorochemicals. Aqueous hydrofluoric acid is prepared by reaction of sulfuric acid with fluorspar (CaF2). Because HF etches glass with formation of silicon tetrafluoride, it must be handled in platinum, lead, copper. Monel (a Cu-Ni alloy developed during the Manhattan Project), or plastic (e.g. polyethylene or PTFE) apparatus. The azeotrope contains 38 % w/w HF and it is a relatively weak acid (pfC 3.18, 8 % dissociation), comparable with formic acid. Other physicochemical properties of hydrofluoric acid are listed in Table 1.2. 

It is usually stated that the corrosive action of hydrofluoric acid, which is readily obtained by the action of sulphuric acid upon the mineral in the warm, was first observed by Herr Swanhardt, an artist of Nuremberg, in 1670. Some accidentally fell on to his spectacles and etched the glass from that time onwards Swanhardt etched glass with the vapours from fluorspar and sulphuric acid. But this pretty legend has been exploded by Partington who... 

Balance the following equation for the reaction of hydrofluoric acid [HF/rj )] with glass, which can be represented as calcium silicate (CaSiOj). Decorative glass is etched using this reaction ... 

H.13 Hydrofluoric acid is used to etch grooves in glass because it reacts with the silica, Si02(s), in glass. The products of the reaction are aqueous silicon tetrafluoride and water. Write a balanced equation for the reaction. 

In order to silver Dewar flasks the jacket is cleaned and filled about two thirds full with the prepared solution. The Dewar should be rolled or shaken during the severing. The end-point is determined by occasionally pouring out a little of the solution, and when a flocculent precipitate is formed the solution should be removed from the flask as quickly as possible to prevent blooming. The flask is then cleaned and dried. If the glass is first etched with a dilute solution (about 0-7 molar) of hydrofluoric acid before its final cleaning, the... 

Hydrofluoric acid is used to etch glass by reacting with the silicates in glass to produce a very volatile and thermodynamically stable compound, silicon tetrafluoride, SiF4. For example,... 

In 1786 M. H. Klaproth published in CrelVs Annalen a method devised by Count von Gesler for etching letters and drawings on glass with hydrofluoric acid (76, 86), and in 1788 Jean-Pierre-Casimir de Marcassus,... 

Etching of Glass with Hydrofluoric Acid. Cover a glass plate with a layer of paraffin. To do this, lower it into paraffin melted in a porcelain bowl and immediately extract it. Make an inscription with a penknife on the paraffin-coated surface so as to uncover the surface of the glass. Make a small paraffin barrier at the edges of the inscription. Pour a 10% hydrofluoric acid solution onto the paraffin-coated plate and let it stand in a fume cupboard. After one or two hours, wash the solution off the plate and remove the paraffin. What happened to the glass Write the equations of the reactions. 

Hydrofluoric Acid. — Evaporate 10 cc. of hydrogen peroxide with a few drops of sodium hydroxide solution, transfer the concentrated liquid to a watch glass, evaporate to dryness on the latter, pour concentrated sulphuric acid over the residue, and allow the whole to stand two to three hours in a warm place. After washing off the glass, no etching should be visible. 

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