The pain in his finger was excruciating. He had never felt anything like this, the professional painter told the emergency room physician. Yet the finger, save for a little white discoloration, looked almost normal. Perhaps there was a small blood clot blocking the circulation, the doctor thought, and started the patient on aspirin. It didn’t do the job. The man was back the next day, his face contorted with pain. But now the finger no longer looked normal; it was red and swollen, and the tip had turned black! It was obviously time for some probing questions. At first, the patient could not think of anything he had done differently, but then he recalled having used a new, heavy-duty cleaning agent a couple of days earlier. In fact, he still had some of it left. A quick perusal of the bottle’s label, and the mystery was solved. The active ingredient was hydro fluoric acid (hydrogen fluoride dissolved in water), one of the most dangerous chemicals you can ever encounter.
Once the culprit was identified, the course of treatment was clear. The application of a 2.5 percent calcium gluconate gel brought instant relief. After three days of such treatment, the finger was as good as new. A lucky man! The fluoride ion released by hydrofluoric acid is terribly corrosive. It penetrates tissues readily and combines with calcium to form insoluble calcium fluoride. Nerve function relies on a balance of calcium and potassium ions, and when calcium is removed, normal conduction fails, and terrible pain ensues. Calcium gluconate counters the problem by quickly replenishing calcium. If a topical application doesn’t help, it can be administered intravenously. Prompt diagnosis of HF exposure is critical because it can cause far more problems than severe pain. Sudden calcium depletion can cause changes in heart rhythm, and can lead to death. One of the most frightening features of hydrogen fluoride exposure is that the skin can look practically normal while the underlying tissues are being eaten away.
Not everyone who has a run-in with hydrofluoric acid is as lucky as our painter. A lab technician who spilled the contents of a small bottle in his lap paid the ultimate price. In spite of immediately hosing himself down and jumping into a swimming pool, he sustained chemical burns on about 10 percent of his body. By the time he arrived in hospital, his blood calcium was dangerously low, and he soon lost consciousness. Circulation in his right leg was lost, and it had to be amputated. Despite valiant efforts, he died of hydrogen fluoride poisoning within two weeks. Had he been wearing proper polyvinyl chloride (PVC) protective apparel, he would still be with us today. But this lab technician most assuredly was not the first to succumb to hydrogen fluoride exposure. Indeed, the years that followed the discovery of HF were filled with such tragedies.
Way back in 1771, the Swedish chemist Karl Wilhelm Scheele was investigating the properties of a mineral known as fluorspar (calcium fluoride). He mixed the pulverized rock with sulfuric acid and heated the mixture. The results were literally staggering! Scheele practically choked on the vapors that were produced, but he survived to make a dramatic discovery. The clear glass vessel in which he had combined the fluorspar and sulfuric acid had become cloudy. Somehow, the glass had partially dissolved! Fluorine forms extremely strong bonds with silicon and strips silicon atoms right out of the silicon dioxide framework of glass. No one before had ever encountered a chemical that could dissolve glass, and now Scheele could produce such a substance on demand. What it could be kept in was the first obvious question. Bottles made of gutta percha, a form of naturally occurring rubber, solved the problem. But another question remained to be answered. Why would anyone want to dissolve glass? Perhaps it was to attract ladies.
“Would you like to come up and see my etchings?” may well be the oldest of all bad pickup lines. Its origins can be traced back to the early use of hydrofluoric acid to etch designs on glass. One shudders to think of all the miseries undoubtedly caused by the cavalier use of such a dangerous substance. But it was not only men who wanted to appeal to the ladies who were interested in etching glass; men who wanted to hide from the gentle sex also saw the appeal of hydrogen fluoride. The Victorian “public house” was the traditional male refuge where drunkenness and raunchy behavior were the order of the day. Clear windows allowed wives and other passersby to witness the debauchery, much to the concern of the revelers. Frosted glass eliminated transparency, and its light-scattering properties made for a very pleasant illumination.
Later, this notion also appealed to lightbulb manufacturers. Clear bulbs produced a great deal of annoying glare. Frosting the bulb with hydrofluoric acid cut down the glare, but the rough surface readily gathered dirt and diminished the light’s intensity. So why not put the frosting on the inside? That was tried, but it weakened the glass. Finally, in 1925, Marvin Pipkin discovered that treating the glass with hydrogen fluoride twice instead of only once paradoxically allowed it to keep its strength. We have been basking in the frosted glow of lightbulbs ever since.
In addition to the glass industry, aluminum, steel, and petroleum manufacturers also use large amounts of HF. They take extensive precautions. This is not always the case with consumers, who really would be better off using other rust removers such as phosphoric acid. Not many realize the terrible dangers of hydrogen fluoride–based rust removers and aluminum cleaners. If they did, they would never dispose of a half-empty bottle of the stuff in a garbage bag. That is just what happened in New York. When sanitation workers threw the bag into the compactor on the truck, they got sprayed with hydrofluoric acid. Despite immediate attention, one of the men died within five hours. Manslaughter charges await the perpetrator, should he ever be caught.