Cleaning hydrofluoric acid

Fluorine, the most reactive element known, is a dangerous material but may be handled safely using proper precautions. In any situation where an operator may come into contact with low pressure fluorine, safety glasses, a neoprene coat, boots, and clean neoprene gloves should be worn to afford overall body protection. This protection is effective against both fluorine and the hydrofluoric acid which may form from reaction of moisture in the air. 

Hydrated amorphous silica dissolves more rapidly than does the anhydrous amorphous silica. The solubility in neutral dilute aqueous salt solutions is only slighdy less than in pure water. The presence of dissolved salts increases the rate of dissolution in neutral solution. Trace amounts of impurities, especially aluminum or iron (24,25), cause a decrease in solubility. Acid cleaning of impure silica to remove metal ions increases its solubility. The dissolution of amorphous silica is significantly accelerated by hydroxyl ion at high pH values and by hydrofluoric acid at low pH values (1). Dissolution follows first-order kinetic behavior and is dependent on the equilibria shown in equations 2 and 3. Below a pH value of 9, the solubility of amorphous silica is independent of pH. Above pH 9, the solubility of amorphous silica increases because of increased ionization of monosilicic acid. 

There are, however, certain acid-based materials which can primarily be construed as cleaners. One such type of material is used in the cleaning of aluminium cans prior to treating and lacquering. Such cleaners are normally based on sulphuric or phosphoric acid, with, generally, additions of hydrofluoric acid and surfactants. These materials are sprayed on to pre-formed cans to remove the lubricant used during the can-forming operation. The fluoride is present to enhance the removal of fines of metal swarf in the cans as well as to remove the oxide film. 

C) for cast iron and up to 140 °F for marstenitic SS (60 °C). It is widely used where silicates are present with the iron oxides. Typically, 5 to 7.5% HC1 is employed. The ammonium bifluoride normally is present at 0.5%, but it may be increased to a maximum of 1.5% for a boiler that has not been cleaned for many years. The presence of hydrofluoric acid (HF), which is formed by the reaction of ammonium bifluoride with HC1 (see equation), tends to increase the rate of iron oxide dissolution and reduce the corrosion rate of exposed steel, when compared to using HC1 alone. This is due to the stability of the hexafluoroferric ion (FeFg3 ), which prevents the ferric ion from corroding exposed steel. 

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... 

The amphoteric agents exhibit excellent compatibility with inorganic electrolytes and with acids and alkalis. Such is their stability in strongly acidic solution that they are even used in cleaning compositions based on hydrofluoric acid [14]. 

Are there any alternative chemicals which can be used to eliminate hazards (e.g., the use of lithium metaborate fusion rather than hydrofluoric acid as a dissolution procedure) The protocol should include details of any required checks on the control measures to be adopted, and their frequency (e.g., cleaning of protective clothing, washing down of fume cupboards). 

Clean slides in a ultrasonic bath with 1% SDS and 4% hydrofluoric acid (HF). 

If the contaminants exhibit a high vapor pressure, then they can be pumped out relatively quickly. If this is not successful, then the apparatus will have to be cleaned. Contaminated glass components will first be cleaned with chromic-sulfuric acid mixture or - if this is necessary - with dilute hydrofluoric acid (1 30). They are then rinsed with distilled water. If this does not bring about the desired results, then an organic solvent can be tried. Then the glass components will again have to be rinsed with methanol and distilled water. (Do not use denatured alcohol )... 

To measure a definite volume of hydrofluoric acid, you can use an ordinary clean and dry glass measuring cylinder whose inner walls have been coated with a thin layer of paraffin. How does hydrofluoric acid react with glass ... 

Electronics Industry Electronics-grade nitric acid (70%) is used by semiconductor and printed circuit board manufacturers. Nitric acid cleans contaminants from the wafer s surface during several steps in semiconductor manufacture. Acetic and hydrofluoric acids may be blended with nitric acid to etch away metal. Nitric acid is also used for cleaning in the manufacture of printed circuit boards. 

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