Hydrofluoric Acid is an acid like no other. It is so potent that contact with it may not even be noticed until long after serious damage has been done. Even very strong acids, and mixtures of acids, like Aqua Forte and Aqua Regia, do not have the power to cause death and injury in the way that Hydrofluoric Acid can.
The Chemistry of Hydrofluoric Acid
Hydrofluoric Acid is the aqueous solution of Hydrogen Fluoride gas. It is manufactured from the reaction of the mineral Fluorspar (Calcium Fluoride) and Sulphuric Acid. It is technically a weak acid, as it has a low degree of free ions, but it is extremely reactive with almost all metals and their oxides.
It is used mainly in the production of Fluorocarbons and Aluminium, metal surface cleaning, and as an etchant for Silicon, Alumina, and glass. It cannot therefore be stored in glass containers.
Safety Precautions when Handling Hydrofluoric Acid
Hydrofluoric Acid should never be handled by anyone who has not been trained to use it. It should be handled under a fume-hood with adequate extraction. Near the fume hood, there should be a fully equipped eye wash and safety shower.
Goggles are absolutely necessary, and should be the type that fully surround the eyes and not just protect against a splash from the front. A plastic face-shield is preferred, provided it does not interfere with safe handling of the acid. Gloves are also essential. Nitrile gloves will provide some resistance to the acid, but thicker gloves made from PVC or Neoprene can be used if they do not impede handling or general dexterity. Finally, an antidote gel for Hydrofluoric Acid should be available within easy reach of the handling area. There are a few suitable gels, but Calcium Gluconate is readily available.
Symptoms of Hydrofluoric Acid Burns
The Hydrogen Fluoride molecule is so mobile that it may easily pass through the skin. Because Fluorine has an extremely high affinity for Calcium, bones will be attacked, and this may result in hypocalcaemia. There may be no pain immediately after the burn, leading the injured person to believe that they are not in danger.
Treatment for Hydrofluoric Acid Burns
Immediately after exposure to Hydrofluoric Acid, it is essential to seek treatment. All affected clothing needs to be removed, and the affected skin area should be thoroughly irrigated with water. Application of a suitable gel like Calcium Gluconate or Calcium Carbonate is then needed. This is important so that the victim's burns do not result in hypocalcaemia.
Summary of Hydrofluoric Acid
Hydrofluoric Acid is an extremely dangerous chemical, and can cause death from a skin exposure of less than 3% of body area. Special training, preparation, Personal Protective Equipment, and handling precautions are needed at all times.
This article is not a substitute for medical advice, Risk Assessments, Chemical Safety Data Sheets, or any other professional service that needs to be used before dealing with Hydrofluoric Acid.
References for Hydrofluoric Acid
Some information in this article was found in "Hydrofluoric Acid Chemical Safety Information" (EHS Dept, UNC), and Hydrogen Fluoride: Etched in History, an article from Canadian Chemical News.
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