Acid hydrofluoric

The hydrofluoric acid is a aqueous Solution very corrosive and poison of Hydrofluoric acid.

Description

The pure hydrofluoric acid is often called acid hydrofluoric anhydrous . The hydrofluoric acid is a Weak acid . Indeed, the connection Fluorine - Hydrogène is relatively strong, so that the dissociation of hydrofluoric acid in water is not total. The hydrofluoric acid reacts with the Verre of silica (SiO₂):

SiO_{2 (S)} + 6 HF_(aq) → H₂_(aq) + 2:00 ₂O_(L)

Consequently, it must be stored in containers in plastic, and even ideally in bottles in Téflon. Hydrofluoric acid with the single property to be able to dissolve all almost the inorganic Oxyde S . In the human body, it reacts with the Calcium and magnesium and can damage the Nerf S, the Os and several bodies among which the Cœur and the Rein S.

Manufacture

On an industrial scale, the hydrofluoric acid is produced starting from the Fluorine (mineral known also under the name of calcium fluoride, of Chemical formula CaF₂) and of Acid sulphuric concentrated. When these two made up is mixed with 250°C, they react to form hydrofluoric acid according to the reaction:

CaF₂ + H₂SO₄ → 2 HF + CaSO₄

The vapor produced by this reaction consists of a mixture of hydrofluoric acid, of sulphuric acid and small quantities of other secondary products, from which the hydrofluoric acid is isolated by Distillation.

Use

Because of its capacity to dissolve the Oxide S, the hydrofluoric acid is an important reagent in the processes of purification of the Aluminum and the Uranium. It is also used to attack the Verre, to eliminate oxides from surface of the Silicium in the industry of the Semi-conducteur S, like catalyst of the reactions of Alkylation of isobutane and butylene in the Raffinage of oil and to eliminate from the oxidized impurities of the Stainless steel.

It is also used during the synthesis many made up organics containing Fluor, among which the Téflon and gases used in Réfrigération like the Fréon.

Safety

This compound is extremely toxic. In the human body, the hydrofluoric acid reacts with the Ion S Calcium and Magnésium. It can damage the bodies whose good performance depends on these ions. The exposure to this acid is not inevitably painful immediately. The symptoms can appear only after several hours, when the acid starts to react with the calcium of the Os. In the majority of the cases, the exposure to the hydrofluoric acid causes serious wounds, even mortals, in particular with the Cœur, the Rein S, the Os and the Foie. In the event of exposure, the head end generally rests on the application of a gel of Gluconate of calcium on the exposed part of the body. If the exposure important or is prolonged, the treatment is based on the injection of a calcium solution directly in a Artère or surrounding fabrics. In all the cases, an immediate doctor visit is necessary. A new immediate processing is the application of Hexafluorine®, a liquid which makes it possible to absorb by contact, quickly and simultaneously the acid ions (H+) and the ions fluorine (F). The capacity of chelation on these ions is quite higher than that of calcium gluconate used usually. Moreover, this solution is hypertonic what makes it possible to stop the progression of the ions fluorine and to decontaminate projection completely.

Even with an immediate medical care, an exposure to minor amounts of acid on less than 10% of the surface of the body can be fatal. Very concentrated solutions can involve an acute Hypocalcémie, followed by an heart attack mortal, and are generally fatal for exposures of about 2% of the surface of the body. The hydrofluoric acid must be handled with important precautions, beyond what is necessary for other acids like the Hydrochloric acid or the sulphuric Acid .

R: 26/27/28 (Very toxic by inhalation, contact with the skin and ingestion.)
R: 35 (Causes serious burns.)
S: 1/2 (To preserve under key and out of reach children.)
S: 7 (To preserve the well closed container)
S: 9 (To preserve the container in a well broken down place)
S: 26 (In the event of contact with the eyes, to immediately wash to consult an ophthalmologist)
S: 36/37 (To wear clothing protective and gloves suitable.)
S: 39 (To carry an apparatus of protection of the yeux/du suitable face)
S: 45 (In the event of accident or Malayan to consult a doctor immediately (if possible to show him the label).

Reference UNO for the Transport of dangerous matters

Class: 8
N° UNO: 1790

3 names according to the concentration:

* ACID HYDROFLUORIC containing more than HYDROFLUORIC hydrofluoric acid 85%

* ACID containing between 60% and 85% of HYDROFLUORIC hydrofluoric acid

* ACID containing with more than hydrofluoric acid 60%

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