Non-combustible, substance itself does not burn but may decompose upon heating to produce corrosive and/or toxic fumes. Some are oxidizers and may ignite combustibles (wood, paper, oil, clothing, etc.). Contact with metals may evolve flammable hydrogen gas. Containers may explode when heated.
Crystallise NaF from water by partial evaporation in a vacuum desiccator, or dissolve it in water, and precipitate ca half of it by adding EtOH. The precipitate is dried in an air oven at 130o for one day, and then stored in a desiccator over KOH. Its solubility in H2O is 4% at 15o and 4.3% at 25o. [Kwasnik in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol I p 235 1963].
ChEBI: A metal fluoride salt with a Na(+) counterion.
Melt immersion method
Calcine the fluorite, quartz sand and soda ash at high temperature (800~900 ℃), followed by water leaching, and then by evaporation, crystallization, drying to prepare products.
CaF2 + Na2CO3 + SiO2 → 2NaF + CaSi03 + C02 ↑
It is derived from neutralization of soda ash or caustic soda with hydrofluoric acid,
2HF + Na2CO3 → 2NaF + H2O + CO2 ↑
Dissolve soda in the pot liquor, and then add 30% hydrofluoric acid to neutralize to a pH value of 8-9, until CO2 gas evolution, hydrofluoric acid often contains fluosilicate impurities, and after neutralization to generate sodium fluosilicate, heating for 1h at 90~95 ℃, sodium fluosilicate decomposes:
Na2SiF6 + 2Na2CO3 → 6NaF + SiO2 + 2C02 ↑
And during the process of neutralization, pH value is not less than 8, otherwise sodium fluoride is difficult to decompose by base, and neutralization solution is allowed to stand for 1h, serum is cooled and concentrated to precipitate sodium fluoride crystals and then separated by centrifugation, drying, crushing to obtain products.
Sodium fluosilicate method
As the byproduct of the wet process of phosphoric acid and phosphate fertilizer, fluosilicic acid may prepare 99.87% sodium fluoride by conventional methods. The reaction lasts 160~180min at 84~95 ℃ and 0.15MPa conditions, with an excess of 5% to 8% alkaline solution (pH value 8-9) to prepare sodium fluoride.
Na2SiF6 + 2Na2Co3 → 6NaF + SiO2 + 2C02 ↑
After standing and clarification of neutralization solution, the supernatant was concentrated by evaporation, cooling crystallization, after separation, wash with hot water of 50~60 ℃, indirectly dry to obtain products.
1. Sodium fluoride is mainly used as Inlaid steel for mechanical blade and planer to enhance weld strength. Secondly, it is used as wood preservatives, fungicides in brewing industry, agricultural pesticides (should be infected with blue), medical preservatives, welding flux, fluorine agent for drinking water. Also used for producing other fluoride and casein glue, sodium fluoride toothpaste, as adhesives, also used in paper and metallurgical industries. In the production of elemental fluorine, it is used for removing trace amounts of hydrogen fluoride. In addition, it is also used in enamels and pharmaceutical industries.
2. Sodium fluoride is used as disinfectants, preservatives, pesticides, also used in enamel, wood preservation, medicine, metallurgy, manufacturing of fluorides and so on.
3. Used for determination of scandium in microanalysis, determination of phosphorus in photoelectric colorimetric analysis, used as reagent, the masking agents, preservatives of iron and steel.
4. As food supplements. According to Chinese regulations for salt, the maximum usage is 0.1g/kg.
5. It is used as wood preservatives, pharmaceutical preservative, welding flux and used in paper industry, this company's products are specific level toothpastes, can also be used as purifying agent for drinking water, and used for hides and skin processing in tanning industry, for smelting and refining of light metal, and protection layer of light metal, for adhesive corrosion, and manufacturing boiling steel.
6. Sodium fluoride is used as the Phosphate accelerator in coating industry, makes phosphating solution stability, phosphate refinement, improves the performance of phosphate coating. Aluminum and its alloys phosphate can close negative catalytic Al3 + of great danger, and make phosphating smoothly. It is used as wood preservatives, agricultural pesticides, fungicides in brewing industry, pharmaceutical preservative, welding flux, alkaline zincate zinc additives and enamel, paper and so on.
Sodium fluoride is an acute toxicant. Ingestion of large quantites (5 to 10g) can cause death in humans. Smaller quantities can produce nausea, vomiting, diarrhea, stupor, and weakness. Other symptoms are tremor, muscular weakness, and dyspnea. Mottling of teeth can occur from chronic exposure.
Sodium fluoride is a colorless crystalline solid or white powder, or the solid dissolved in a liquid. Sodium fluoride is formed by the reaction of sodium carbonate and hydrofluoric acid. Sodium fluoride is soluble in water. Sodium fluoride is noncombustible. Sodium fluoride is corrosive to aluminum. Sodium fluoride is used as an insecticide. Sodium fluoride is also used to fluorinate water supplies, as a wood preservative, in cleaning compounds, manufacture of glass, and for many other uses.
It is colorless crystals or shiny white powder, belongs to tetragonal system, is positive hexahedral or octahedral crystals. It is slightly soluble in alcohol, soluble in water. Aqueous solution is acidic. It dissolves in hydrofluoric acid to form sodium hydrogen fluoride.
Hazards & Safety Information
Toxicity grading: Highly toxic
Oral-rat LD50: 52 mg/kg; Oral-Mouse LD50: c57 mg/kg
Eyes-rabbit 20 mg/24 hours moderate
Flammability hazard characteristics: It is non-combustible. In case of acid, it releases toxic hydrogen fluoride gas, heating may produce toxic fumes of fluoride and sodium oxide.
Storage Characteristics: Treasury ventilation low-temperature drying, stored separately from oxidants, food additives.
Occupational standards: TLV-TWA 2.5 mg (fluorine)/cubic meter, STEL 5 mg (fluorine)/cubic meter
Fluorinse (Oral-B); Minute-Gel (Oral-B); Neutra Care (Oral-B); Pediaflor (Ross).
Ingestion may cause vomiting, abdominal pain, diarrhea, convulsions, collapse, thirst, disturbed color vision, acute toxic nephritis.
Solubility in water
Dissolved Amount per 100 ml of water at different temperatures (℃) in grams:
3.66g/0 ℃; 4.06g/20 ℃; 4.22g/30 ℃; 4.4g/40 ℃
4.68g/60 ℃; 4.89g/80 ℃; 5.08g/100 ℃
Application in toothpaste
Sodium fluoride was added to toothpaste which can play against dental caries, since enamel interacts with fluoride to form fluorapatite on the enamel surface, which improves the hardness and acid resistance of enamel, and reduces formation of plaque, reduces the incidence of dental caries.
Fluoride toothpaste does have some anti-caries effects. As early as the mid-19th century, pregnant women took orally calcium fluoride for anti-caries in Europe. In the 20th century, fluoride is recognized worldwide as an effective anti-caries agent. Usually in fluoride toothpaste, the content of sodium fluoride is 0.22-0.33%, the content of sodium monofluorophosphate is 0.76%. Although small amount, it has a good protective effect on people's teeth, can reduce the caries prevalence rate of 28%.
According to different content of fluoride in toothpaste, fluoride toothpaste is divided into the following categories: sodium fluoride toothpaste, monofluorophosphate toothpaste, stannous fluoride toothpaste, amine fluoride toothpaste and so on. Currently the most common fluoride toothpaste on the market are sodium fluoride toothpaste and monofluorophosphate dentifrice, or double fluorine toothpaste containing both sodium fluoride and sodium monofluorophosphate. Different types of fluoride toothpastes, and whether the toothpastes contain single fluorine or double fluorides, their effects of anti-caries are the same.
As insecticide, particularly for roaches and ants; in other pesticide formulations; constituent of vitreous enamel and glass mixes; as a steel degassing agent; in electroplating; in fluxes; in heat-treating salt compositions; in the fluoridation of drinking water; for disinfecting fermentation apparatus in breweries and distilleries; preserving wood, pastes and mucilage; manufacture of coated paper; frosting glass; in removal of HF from exhaust gases to reduce air pollution. Dental caries prophylactic.