Hydrofluoric acid is most often produced in the form of a 40% solution, but sometimes 50% and even 72% solutions are found. It is also called hydrofluoric acid or an aqueous solution of hydrogen fluoride. Its name was formed from fluorspar, from which, in turn, hydrogen fluoride is obtained.
Hydrofluoric acid is the formula for its HF. Visually, it is a colorless liquid, has a molar mass of 20.0063 g / mol and a density of 1.15 g / cm³. It is characterized by temperatures: melting - 83.6 ° C, boiling - 19.5 ° C. It is non-combustible and very toxic.
What features does hydrofluoric acid have? The formula of this substance suggests that it contains fluorine and hydrogen. It belongs to the second class of danger, since fluorine formed during dissociation is toxic and dangerous to our environment.
When this acid is dissolved in water, heat is generated in an amount of 59.1 kJ / mol. It reacts with many metals, forming fluorides. An interesting fact is that even a small part of this acid can lower the standard freezing point of water. At low temperature, hydrogen fluoride forms the following compound with water, H2O · HF, H2O · 2HF and H2O · 4HF.
Despite the fact that hydrofluoric acid is an acid of moderate strength, it corrodes glass and silicate containers. In addition, it is the only substance from its class that interacts with silicon oxide SiO (2). This oxide, in turn, is the main material used to produce glass. Hydrofluoric acid does not affect paraffin, so it is widely used during its storage. Currently, it is transported and stored only in plastic packaging or in containers made of rubber and lead. High concentration (60%) acid can be transported in durable containers made of steel.
Metals that do not dissolve in it are: lead, platinum and gold. Technical hydrofluoric acid contains several impurities, among which the most common are Fe, Rb, As, and also H2SiF6, SO2. Good purification of the acid is obtained by converting it to potassium hydrodifluoride. Then it is decomposed by heating and hydrogen fluoride is dissolved in water.
When working in laboratories, utensils and containers made of polyethylene and teflon are used, and large volumes of hydrofluoric acid are stored in steel, tight, hermetically sealed tanks, as well as in tanks or in ammonia-type cylinders, which necessarily have a protective color.
Hydrofluoric acid is hazardous to human health. She has a weak narcotic effect on the psyche. If for some reason it has got into the blood, in this case a severe form of poisoning with a change in the functions of the digestive system and pulmonary edema cannot be avoided. Even hydrofluoric acid can lead to disruption of the heart and general intoxication of the body.
If it comes into contact with the skin or eyes, it causes painful burns even at low concentrations. Especially unpleasant are the consequences of penetration of acid under the nails, therefore it is necessary to work with it only with gloves and under a good hood.
If acid does get on your skin, rinse it immediately under running water and treat it with 2.5% calcium gluconate as a gel. But you can not stop there, you should immediately consult a doctor. He will prescribe intravenous injections with calcium chloride.
Where is this dangerous acid used? Currently, it is actively used in the destruction of rocks from silicate, for the dissolution of metals such as niobium, tantalum and zirconium. It acts as a catalyst in the hydrogenation and dehydrogenation, as well as in the production of fluoroplastics, chladones and fluorosulfonic acid. She found her application in the oil industry. It is treated with oil wells to increase oil production.