Sodium fluoride is an inorganic compound, a s alt of hydrofluoric acid and sodium. It is a white, odorless crystalline substance. The chemical formula of sodium fluoride is NaF. Chemical bond - ionic.
Spread in nature
In nature, this substance exists mainly in the form of the mineral williomite. This mineral represents sodium fluoride in its pure form. It can have a very beautiful color from carmine red, pink to colorless. It is quite brittle and relatively unstable. The brilliance of this mineral resembles the brilliance of glass. Its deposits are found in North America, Africa and the Kola Peninsula, but in general it is quite rare.
Obtained by industry
Sodium fluoride is a rather useful compound, so it is synthesized on an industrial scale. World production is over 10,000 tons per year. In most cases, the raw materials are hexafluorosilicates, which are also obtained artificially. In production, they are subjected to alkaline hydrolysis, as a result of which sodium fluoride is released in the reaction mixture. But it still needs to be separated from impurities of silicon oxide and sodium silicate. Dothis is often just plain filtering.
But hexafluorosilicates, even when thermally decomposed or when interacting with sodium carbonate, can give sodium fluoride. It can also be used in industrial synthesis.
Also in industry there is a method for obtaining sodium fluoride from soda ash (sodium carbonate) and hydrofluoric acid. As a result of their interaction with the help of filtering, it is possible to obtain a technically pure product:
Na2CO3 + HF → 2NaF + CO2 + H 2O
Laboratory Obtaining
In the laboratory, there are other ways to obtain this compound. The simplest is the reaction of neutralization of sodium hydroxide with hydrofluoric acid. Another option: the interaction of sodium hydroxide with ammonium fluoride. Sodium hydroxide can also give fluoride when interacting with simple fluorine.
In theory, sodium fluoride can also be obtained from simple substances: sodium and fluorine. This reaction proceeds very violently, although in practice it is carried out very rarely.
F2 + 2Na → 2NaF
Another way to obtain is the thermal decomposition of difluorohydrate and some complex s alts. In this case, a product of very high purity is obtained.
Na(HF2) → NaF + HF
When oxidizing simple fluorine with sodium bromate or other oxidizing agents containing sodium as a productmay produce sodium fluoride.
F2 + NaBrO3+ 2NaOH → NaBrO4 + 2NaF + H 2O
By reacting boron trifluoride with sodium hydride, this s alt can also be obtained.
BF3 + NaOH → Na3BO3 + NaF + H 2O
Physical properties
Sodium fluoride is a white crystalline solid. Melting point - 992°C, boiling point - 1700°C. Not hot. Since the chemical bond of sodium fluoride is ionic, it is highly soluble in water, and even better - in hydrogen fluoride. Almost insoluble in organic solvents. Non-hygroscopic and does not form crystalline hydrates.
Chemical properties
In aqueous solutions, sodium fluoride dissociates and forms a complex compound.
NaF + 4H2O → [Na(H2O)4] + + F-
When interacting with hydrofluoric acid, difluorohydrate is formed. But with an excess of hydrogen fluoride, other complex compounds can be formed, which are called sodium hydrofluorides. Their composition may be different depending on the ratio of reagents.
As you can see from the chemical formula, sodium fluoride is a typical s alt, so it enters into exchange reactions with other s alts if a precipitate or gas is formed as a result of the reaction. When interacting with acids, gaseous hydrogen fluoride is released. And with lithium hydroxide, a precipitate of lithium fluoride is formed.
Sodium fluoridemay form other complex s alts, depending on reagents and reaction conditions.
Toxicity
Sodium fluoride is a dangerous substance. It has the third level of danger out of four according to the NFPA 704 standard. The lethal dose for humans is 5-10 grams. This is quite a lot, but even smaller doses of sodium fluoride harm the cardiovascular system. Poisoning can occur both by inhalation of poisoned air, and by ingestion of this inorganic compound in food. In the latter case, stomach irritation can occur, up to an ulcer.
Application
Sodium fluoride has good antiseptic properties, so it is sometimes added to detergents. For the same reason, it is used for wood processing. A solution of this s alt helps fight mold, fungus and insects. Most often, a three percent solution is used. It penetrates well into the wood and protects it from decay. But this remedy has a drawback, because of which sodium fluoride is rarely used - it is easily washed out of the wood during rains, since this s alt is highly soluble in water.
It is also used in the synthesis of some chemical compounds, in particular freons and insecticides. Fluorine ions stop glycolysis (glucose oxidation), so sodium fluoride is used for biochemical research.
It is also often used in the metallurgical industry for cleaning metal surfaces, as well as during their melting and soldering. The substance is sometimes added to cement, making concrete resistant toto acids, and in lubricants to improve heat-resistant qualities.
Its most controversial use is in toothpastes. For teeth, sodium fluoride is a source of fluorine, which is necessary to give bones and teeth strength, and also serves to prevent caries. But with a high consumption of this element, negative consequences can occur. Therefore, there is still debate about the use of fluoride as an additive in toothpaste.
The positive effect of fluoride on the body
Fluorine is a rather important trace element in the human body, without which its normal life is impossible. It is necessary to consume 0.03 mg of fluoride per kilogram of body weight per day for an adult. The child needs 5 times more.
The functions of fluorine in the body are very diverse. It contributes to the proper growth and formation of bones, hair and nails, as it stabilizes calcium in the process of mineralization. This is especially important during the growth and development of children, as well as fractures. This element is necessary to maintain immunity. Iron is better absorbed by the body if fluoride is involved in this process.
With a lack of this element, tooth enamel is weakened, the risk of caries increases. In children in this case, defects may appear during the development of the skeleton. Adults are at risk of developing osteoporosis. This disease is characterized by low bone density, which increases bone fragility.
Problems with excess fluoride in the body
With an increased content of fluorine inthe body may develop fluorosis. This disease is characterized by a number of irreversible consequences. In the initial stages of the development of the disease, tooth enamel suffers. On it there are spots of different shapes and colors. Spots are easily diagnosed by a dentist, and with timely treatment, they can be easily removed. For bleaching, solutions of inorganic acids, a solution of hydrogen peroxide, or solutions of other peroxides are often used. After whitening the enamel, remineralization is carried out with a solution of calcium gluconate. In the treatment of more severe forms of fluorosis, it is recommended to take calcium gluconate orally until the end of therapy. If erosion of tooth enamel occurs during fluorosis, then composite materials are used and the shape of the tooth is restored, approximately the same as with filling.
As a preventive measure for this disease, you can reduce the intake of fluoride into the body if its concentration in drinking water is high. To do this, they usually replace the water source or simply filter it. You can also remove foods that contain a lot of fluoride from the diet: sea fish, animal oil, spinach. Eating vitamins C and D and calcium gluconate may help.
If excess fluoride is observed over a long period (10-20 years), bones begin to suffer. Osteosclerosis occurs, in which, unlike osteoporosis, bone density becomes higher than normal, which leads to a decrease in their elasticity. It can also cause frequent fractures. But you shouldn't worry. Such a strong excess of fluorine in the body can only occur in people working onfluoride production without safety precautions.
Water fluoridation
As mentioned above, fluoride can be used to prevent caries. For this reason, in the middle of the last century, fluoridation of tap water began to be used in some countries. Its essence resembles chlorination. A small amount of sodium fluoride or another component containing fluorine is added to water to give it certain properties. Today, 2/3 of all water in the US is fluoridated.
In order for a person to receive the required amount of fluorine, according to the World He alth Organization, drinking water should contain 0.5-1.0 mg of fluoride per liter. But ordinary water does not always contain this amount, so you have to increase it artificially.
Water fluoridation does not affect its taste or smell in any way. Thanks to this process, the risk of caries is greatly reduced, especially among children. This is because fluoride destroys bacteria that can dissolve tooth enamel and cause cavities.
Of course, an increased content of fluorine can lead to fluorosis, but, according to authoritative studies, water fluoridation cannot be the cause of this pathology. Other side effects of such water are also not observed. Although recently some low-quality studies have begun to appear that suggest otherwise. Gaining popularity and the myth that water fluoridation is a way to dispose of fluorides, which are a waste of aluminum enterprises. But this version was not confirmed.
Usefluoridated water is not recommended only for certain diseases: diabetes, hormonal disorders, arthritis, thyroid, kidney and heart diseases.
In any case, water is easy to get rid of the presence of fluorine. Filters working on the principle of reverse osmosis remove almost all fluorine, and distillation purifies water from it completely. Household filters can also partially or completely retain fluorine in themselves. Passing water through alumina, bone meal or bone charcoal can also remove fluoride from the water. Some fluorides (such as calcium fluoride) are insoluble in water, so a precipitation method can be used to precipitate all the fluorine. Lime is often used for this.
Pharmacological applications
Sodium fluoride is an active ingredient in some drugs. As a rule, such tablets are taken as prescribed by a doctor, sometimes therapy requires special monitoring and is accompanied by regular studies of the flow dynamics. Trade names of fluorine preparations: "Sodium fluoride", "Natrium fluoratum" and "Ossin". They are prescribed for a lack of fluoride in the body, in particular for osteoporosis.
The drug in the form of dragees and tablets is taken orally. Almost all fluoride is absorbed by the body, regardless of food intake. Typically, such therapy is combined with the intake of calcium and magnesium, 1-1.5 g per day. This helps the bones to mineralize more consistently.
But the drug is dangerous to take over the norm. In this case, an excess of fluorine may occur, leading to fluorosis. Attaking medicines containing sodium fluoride, it is necessary to see a dentist to prevent the development of fluorosis.
