Hydrofluoric acid is an aqueous solution of hydrogen fluoride gas, which is colorless and transparent to light yellow smoke. Irritating smell. The molecular formula HF · H2O. The relative density of 1.15 ~ 1.18. The boiling point was 112.2 ° C (38.2% by weight). Commercially available concentrations are typically about 47%. With weak acidity, but when the concentration of ionization is greater than when the weak and generally weak electrolyte is different. Corrosive, teeth, bone damage is more serious. Strongly corrosive to silicon compounds. Should be kept in a sealed plastic bottle. Prepared by the absorption of hydrogen fluoride gas. Mainly used as analytical reagents, high purity fluoride preparation, glass etching and electroplating surface treatment.

Physical properties

1, hydrofluoric acid is very volatile, set the air, that is, white smoke.

2, hydrofluoric acid is not combustible, but with most of the metal reaction, resulting in hydrogen and cause an explosion. Case H Blowing agent burns immediately.

3, hydrofluoric acid is highly dangerous poison, touch the skin easy to cause ulceration, if inhaled its vapor, can be fatal.

Chemical properties

Hydrofluoric acid

1, hydrofluoric acid can be with the general metal, metal oxides, and hydroxide role, resulting in a variety of salts, but the role of less severe as hydrochloric acid. Gold, platinum, lead, paraffin and some plastic (polyethylene, etc.) does not work with it, so it can be used as a container.

2, highly corrosive, can erode glass and silicate to generate gaseous silicon tetrafluoride. Glass is a compound of silicon, so hydrofluoric acid can not be contained in glass containers. The reaction is as follows: SiO2 + 6HF → H2 [SIF6] + 2H2O.

3, hydrofluoric acid can form acid salt. Hydrofluoric acid is a monobasic acid, but can produce a series of acid salts, such as NaHF2, KHF2, NH4HF2 and other hydrohalic acid.

4, weak acid of hydrofluoric acid. In hydrohalic acid, only hydrofluoric acid is a weak acid (its ionization constant is 3.5×10 ^ -4, its apparent ionization is 10% at a concentration of 0.1mol1.L ^). The high concentration of hydrofluoric acid is a strong acid because of the following reaction: 2HF → H + FHF.

Due to the ability of hydrofluoric acid to dissolve oxides, it plays an important role in the purification of aluminum and uranium. Hydrofluoric acid is also used to etch the glass, clean the residual sand on the cast, control the fermentation, electrolash and clean the corrode semiconductor wafers. In the refinery it can be used as a catalyst for the alkylation of isobutane and butane, and hydrofluoric acid is also used during the removal of oxygen-containing impurities on the surface of stainless steel. Hydrofluoric acid is also used in the synthesis of a variety of fluorine-containing organic compounds, such as Teflon (polytetrafluoroethylene), Freon class of refrigerant.

Health Hazards

Hydrofluoric acid burns

Hydrofluoric acid has strong irritation and corrosiveness to the skin. Hydrogen ions in hydrofluoric acid have dehydration and corrosion effects on human tissue, and fluoride is one of the most active nonmetallic elements. Skin and hydrofluoric acid contact, fluoride ions continue to dissociate and penetrate into the deep tissue, dissolve the cell membrane, causing epidermis, dermis, subcutaneous tissue and even muscle liquefaction necrosis. Fluoride also interferes with the activity of the enolase to inhibit the oxygen uptake of skin cells.

Skin contact with high concentrations or more than 40% of the concentration of hydrofluoric acid pain immediately occurred, local skin early flushing, immediately turned into gray marble, and then tissue liquefaction necrosis was pulp-like, if not timely treatment can be deep bone, causing bone Aseptic necrosis. When exposed to low concentrations (<40%) of hydrofluoric acid, there may be numbness and ants. Skin contact local initially found as local erythema, quickly turned around to flush white edema or blisters, nail parts were gray black, floating. Concentrations of less than 20% -3% of hydrofluoric acid cause irritating pain and delayed pain.

Eye hydrofluoric acid burns showed bulb conjunctival edema, bleeding, cornea can quickly form a white pseudomembranous opacification, matrix edema, recurrent epithelial erosion, shedding, treatment can not cause perforation.

Inhalation of high concentrations of hydrofluoric acid mist can cause toxic pulmonary edema, hand, foot and convulsions, arrhythmia, hypocalcemia, hypomagnesemia, hyperkalemia, severe ventricular fibrillation, and even cause reflex asphyxia.

Hydrofluoric acid can also be absorbed by the skin and cause serious poisoning. Human intake of 1.5g hydrofluoric acid can cause immediate death.

Emergency treatment

1, skin contact: immediately remove the contaminated clothing, with a large number of mobile water rinse thoroughly at least 15 minutes, as soon as possible to dilute and rush to hydrofluoric acid. Medical treatment. The following are the same as the "

2, eye contact: immediately lift the eyelid, with a large number of mobile water or saline thoroughly rinse for at least 15 minutes. Medical treatment. The following are the same as the "

3, inhalation: quickly from the scene to the fresh air. Keep the airway open. If breathing is difficult, give oxygen. Such as breathing to stop, immediately artificial respiration. Medical treatment.

4, ingestion: mouthwash with water, to drink milk or egg white. Medical treatment. The following are the same as the "

Protective measures

 

1, closed operation, pay attention to ventilation. Operation as mechanized as possible, automated.

2, the operator must be specially trained, strictly abide by the operating procedures. When exposed to smoke, wear a self-priming filter respirator (full cover) or air respirator. Emergency rescue or evacuation, it is recommended to wear oxygen breathing apparatus. Wear rubber acid clothes, gloves, shoes and so on. The following are the same as the "

3, the workshop to install the shower and eye wash equipment, so that the skin, eye pollution can be washed in time. Work finished, shower dressing. Separately store contaminated clothing, wash back.

4, the work site prohibits smoking, eating, drinking water, drinking drinks.

5, to maintain good health habits. Regular physical examination, urinary nitrogen measurement and bone X-ray examination.