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Fluorine inorganic compound and hydrofluoric acid
- Jan 03, 2019 -

Fluorine is known as the most reactive element. It seems dangerous, but it can be seen everywhere around us. This is because chemists have turned them into safe substances. The next few episodes we will see. See how chemists step by step to turn fluorine into a safe and useful thing around us.


First of all, of course, the fluorine gas is taken out from the ore of nature. We already know that there is a better and safer method for preparing fluorine gas in the laboratory. First, the potassium permanganate is treated with hydrogen peroxide or potassium fluorohydride to obtain fluorine. Potassium manganate, and then potassium fluoromanganate and "super acid" antimony pentafluoride reaction, you can get fluorine gas.


The above method is too expensive and uneconomical, so the current industrial production still uses the Moissan electrolysis method, but the protective measures are already much better. A passivation process was invented, and the passivated stainless steel bottle can safely store fluorine gas, and it can also be made of a safer Monel copper-nickel alloy.


Modern fluorine gas storage devices, although I still feel scared, I dare not approach.


Fluorine is used in large quantities to make sulphur hexafluoride, a very heavy gas that is more than four times heavier than air, so if you store this gas in a container, it won't escape. If you put a thin piece of foil on it, the paper will float on the gas and won't fall, which can be used to magic.


Sulfur hexafluoride is a very heavy gas, and a tin foil boat can be easily suspended.


Because it is heavy, if you inhale this gas, it will make your vocal cords particularly thick. We really do not recommend that you do such an experiment. Although sulfur hexafluoride is non-toxic, the impure industrial sulfur hexafluoride will contain toxic gases such as hydrogen fluoride.


What is really useful for sulphur hexafluoride is that it has particularly good insulation properties, so it is used to fill in electronic equipment such as transformers and used as circuit breakers. We can see it in high-voltage switches, large-capacity transformers, high-voltage cables and other places.


Sulfur hexafluoride is used in transformers.


Say something more fluorine, that is the atomic bomb! At the earliest time, the nuclear material of the atomic bomb was uranium. The natural isotope of uranium was uranium 235 and uranium 238. Uranium 238 was a stable isotope, and uranium 235 was prone to fission, but the proportion of uranium 235 in nature was only 0.7%. If an atomic bomb is to be produced, it is necessary to separate uranium 235 from uranium 238 to obtain "highly enriched uranium" with higher purity of uranium 235.


Uranium 235 and uranium 238 are almost identical in nature, with the slight difference being their atomic mass, which differs by only 1.3%. For scientists, such "huge" differences are enough to separate them. If a gas of uranium or uranium compounds is available, different masses of uranium isotopes can be separated by centrifugal force.


Uranium is a very heavy solid with a boiling point of more than 3,700 degrees. It is obviously energy consuming to heat the uranium to a gas form. Its fluoride uranium hexafluoride has a boiling point of only 60 degrees, which is really a good thing, so the uranium is first oxidized into uranium hexafluoride, and then separated by a centrifuge. This gives 80% uranium 235 highly enriched uranium.


In 2008, Iranian President Mahmoud Ahmadinejad was visiting their uranium enrichment unit.


Fluorine has only one stable isotope, 19F, which allows it to be used for MRI.


Another isotope, 18F, is a good source of positrons and is commonly used in the synthesis of positron emission tomography (PET) tracers. At present, the most commonly used tracer in the clinic, fluorine-18-deoxyglucose (18F-FDG), is a tracer containing fluorine-18.


18F is used in radiotracers and has a half-life of about 2 hours, which is sufficient from production to use.



Hydrofluoric acid is a more important raw material than fluorine. It is relatively easy to obtain hydrofluoric acid, and it is obtained by heating sulfuric acid and fluorite to 700 degrees.


Hydrofluoric acid is a weak acid, but it is a particularly corrosive acid, especially for oxides and glass. Its nature allows us to etch glass, and the beautiful pattern on the glass is made with hydrofluoric acid. By the same token, hydrofluoric acid can also be used to etch the surface of silicon semiconductors or to help clean the surface of steel and remove some oxides.


The pattern on the surface of the glass is made with hydrofluoric acid.


Hydrofluoric acid is extremely dangerous for the human body. Fluoride ions enter the blood or tissue to bind to calcium and magnesium ions, making them insoluble or slightly soluble calcium fluoride and magnesium fluoride. If the amount is large, the blood vessels are directly blocked; the hydrofluoric acid has a particularly strong permeability, and it will be in contact with the skin. Rapidly penetrates the stratum corneum, infiltrates into deep tissues, dissolves cell membranes, causes tissue liquefaction; in severe cases, it can reach the periosteum and bone, making bones become calcium fluoride, forming a slow healing ulcer.


On December 27, 2013, students from a middle school in Langxi County, Anhui Province, under the leadership of teachers, conducted extraction experiments and carved glass corrosion experiments. During the experiment, many students were contaminated with hydrofluoric acid and felt unwell afterwards. Seven students were involved. Was sent to the Nanjing Military Region General Hospital for treatment.


Here we can only sigh our educators for ignoring safety. We must know that in factories and laboratories that are exposed to hydrofluoric acid, workers and laboratory workers must be fully armed with masks, gloves and lab coats. There are sprinklers in the workshop or in the laboratory. Although, in my article, I have been telling you about the fearlessness of chemists when facing problems, but now, the seniors have used blood and tears, even life to let us know which are safe and which are risky. The risk is too ignorant, that is, the ignorant is fearless.


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