PowerLabs Hydrofluoric Acid Demo:

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Introduction:

   Hydrofluoric Acid is quite possibly the most dangerous chemical deal with in PowerLabs. Spilling 70% HF over 2% of the body area will very easily result in death the acid destroys tissue, decalcifies bone, and poisons the nervous system. Spills as small as 100mL have resulted in death, despite amputation of the exposed limb and immediate treatment with calcium gluconate; the small molecular size of the acid makes it penetrate skin and fat very quickly, and once it is in the blood it will act as a poison. The high concentration acid also outgases pure HF extensively, and inhalation of as much as a single lungfull of that gas will result in almost certain death by pulmonary edema. To make things worst, HF can also eat through most gloves.
 Although very dangerous, HF acid finds a variety of uses in Industry, from the vital etching of semiconductors to make microchips to chemical analysis for SiO2 to frosting glass, cleaning metals and much more... PowerLabs acquired a bottle of HF to remove the label on a large plasma globe. Although I never got around to it, some interesting uses were found for the chemical as far as its properties in dissolving glass go. Glass is usually thought of as being chemically indestructible (a glass bottle will remain in a landfill for thousands of years), so it is quite impressive to see how it can vanish in a matter of seconds when immersed in this powerful acid.
 

Materials:

Reactants:

 Materials:

Industrial Grade maximum strength (70%) Hydrofluoric Acid (HF(aq))

Test Tube

Distilled Water bath.

Polyethylene Syringe

 

PP Beaker

 

Clamps

 

Procedures:

  A polypropylene beaker is filled with ice cold water and placed under a 20x200mm thermo resistant test tube which is held in place just a few mm above the water by a clamp. 10cc of 70% hydrofluoric acid are then removed from a Teflon bottle and injected into the test tube. For this demonstration a twin filter activated carbon gas mask was used, along with chemical goggles and nitrile gloves.
 

Results:

 The test tube is removed whilst still fuming from the reaction. The Hydrofluoric acid goes into the test tube and begins reacting. 30 seconds later (these 30s were removed from the video to make the file smaller) the energy released by the reaction heats the acid to a boil (112C), which is very, very bad because highly toxic and corrosive fumes of HF shoot out of the test tube. The reaction had to be immediately aborted before the entire room became contaminated with lethal levels of HF gas. In previous experiments with larger acid batches (which have enough heat capacity not to boil) it was found that a test tube will fully dissolve in under a minute at room temperature. The one in this video broke during handling afterwards as its walls became too thin, but did not dissolve completely as was hoped.
 

Relevant Links:

Hydrofluoric acid safety

 
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