Monday 3 June 2013

Little Dog & Hydrofluoric Acid

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Hydrofluoric acid is really nasty stuff. I was very lucky whilst preparing this acid in my shed, aged eleven or so. I was following the directions in my 1854 copy of "The Young Man's Book of Amusements" to produce Very Beautiful Artificial Petrifactions. Note that hydrofluoric acid was known as fluoric acid in the olden days.

As with virtually all of the experiments in the book, no warnings are given about the potential hazards. I was aware that hydrofluoric acid (HF) was more dangerous that nitric, sulphuric and hydrochloric acids. I'd received some nasty burns from the latter acids, whilst on a practical chemistry learning curve of entirely self educated experimental mayhem. Since I was using concentrated sulphuric acid in the procedure, the respect I showed for it probably saved me from finger loss or death, should I have come in contact with the hydrofluoric.

The sinister nature of hydrofluoric acid burns is not just its very corrosive action on the skin. You can be splashed with the stuff and not notice for some time. The HF interferes with nerve function, so no pain is felt as it diffuses quickly through the skin layers (due to it being lipid-soluable, having a low dissociation constant). Only when flesh destruction starts does the excruciating pain begin. By then its too late to do much in terms of flushing and neutralising the acid. It's in your body. Not only will horrific deep burns result, but the chance of death is high. It's a contact poison. If the splash was over a large area of skin (25 square inches or more), the HF causes serious systemic toxicity from interference with blood and tissue calcium levels. In the body, hydrofluoric acid reacts with the biologically important ions Ca2+ and Mg2+. Formation of insoluble calcium fluoride is the proposed etiology for both precipitous fall in serum calcium and the severe pain associated with tissue toxicity. Eventually cardiac arrest and fatality can result.

HF burns.
Photo Dr. Charles Eaton

The lethal nature of hydrofluoric acid was demonstrated in the 19th Century when some heartless bastard killed a poor little dog with six drops of the stuff. It is alluded to in the following quote from Gay-Lussac & Thenard, and described in the final excerpt, the preparation of fluoric acid from "Chemistry for Beginners."

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Unrelated to this post, below is an example of
eclectic science esoterica 

 Nuclear-powered aircraft carrier USS THEODORE ROOSEVELT, cost, 4.5 billion dollars.
Experimental test blast on an big boat.
The shock wave did no damage.
Nice experiment.

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