Glass etched with acid

Put a mixture of 5 g of calcium fluoride and 1 g of calcium sulphate into lead vessel 1 (Fig. 57). Put a paraffin-coated glass plate with an inscription onto lead support 2 with the inscription downward. Pour 5 ml of concentrated sulphuric acid onto the calcium fluoride and cover the vessel with its lead lid. In an hour, extract the plate with tongs, thoroughly wash it with water, and remove the paraffin. How does the surface of glass etched with gaseous hydrogen fluoride... 

Step 2 Where exposed, the metal and photoresist can be removed and the glass etched with buffered hydrofluoric acid. 

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... 

Ammonium Fluosilicate (Cryptohalite), (NH4)2SiF6 mw 178.17 wh crystn pdr sp 2.01, mp — sublimes sol in ale w. Can be prepd by interaction of Amm hydroxide with fluosilicic acid, followed by crystn. Used for glass etching, casting of light metals and electroplating... 

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. 

A typical procedure for etching glass involves covering the glass surface with a mask—a protective coating. The mask is then removed from the areas that are to be etched, and a paste made of fluorite and sulfuric acid is placed on the surface. From standard reference sources, determine the chemical formula of fluorite and describe the chemical reactions that take place to achieve the etching. 

The residue from the treatment with dilute ciel may jdW-be tested for hydrofluoric acid by the ordinary glass-etching method. 

Fig. 4. (a) Schematic diagram illustrating the fabrication process for nanochannel glass array (Tonucci et al, 1992). (b) SEM image of a glass array with 33-nm channels after acid etching (Tonucci et al, 1992). 

The second method of developing surface cracks is to expose the surface to hot sodium vapour.1 With various kinds of glass, this treatment produces visible markings (Fig. 45). It is interesting that neither the metallic films nor the sodium vapour show scratches or drawing marks etching with hydrofluoric acid, on the other hand, shows scratches, but does not show the Griffith cracks,2 as Andrade has called them. 

Berg s divers for example, were hollow glass eontainers that contained mercury to give the desired density. The density was then adjusted to the desired value by etching with hydrofluoric acid. Various modified divers were later developed, the final ones, by Kaye and James [57], being metal coated polythene spheres which were located with search coils. 

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