Sodium fluoride

Sodium fluoride (SO-dee-um FLOR-ide) is a colorless to white crystalline solid or powder. It is best known for its role in efforts to prevent tooth decay. It may he added to toothpastes or mouthwashes or to municipal water supplies for this purpose. Although the practice of fluoridating water is now widespread in the United States, it remains the subject of controversy regarding its potential health effects on humans. 

Sodium fluoride occurs naturally as the mineral villiau-mite, although the compound is not produced commercially from that source. Some sodium fluoride is obtained as a byproduct of the manufacture of phosphate fertilizers. In that process, apatite (a form of calcium phosphate that also contains fluorides and/or chlorides) is crushed and treated with sulfuric acid (H2S04). The products of that reaction include phosphoric acid (H3P04), calcium sulfate (CaS04), 

Sodium fluoride. Green atom Is fluorine and turquoise atom is sodium, publishers 

More than 50 years of research has shown that sodium fluoride and other fluorides are effective in preventing tooth decay. Based on this information, sodium fluoride or some other compound of fluorine is now added to most toothpastes made in the United States. Dentists regularly treat their patients teeth with fluoride washes to make them more resistant to decay. Most cities and towns in the United States add sodium fluoride or a comparable compound to the municipal water supply to reduce the rate of dental caries (cavities). Some people who live where fluoride is not added to their water supply take sodium fluoride pills to improve their dental health. The American Dental Association and the World Health Organization recommend 

In spite of these trends, opposition to the use of fluorides against tooth decay remains strong in the United States and other parts of the world. Opponents are not convinced that there is sufficient evidence for the claims that fluoridation decreases the rate of tooth decay. They suggest that fluorides may cause cancer and a host of other health problems. And they argue that fluoridating public water supplies removes the choice that individuals should have as to whether or not they want to use fluorides in their dental health program. 

INTRODUCTION This data sheet summarizes properties of sodium fluoride single crystals. 

Transmission Region, (External Transmittance 10% with 2. 0 mm. thickness) 0. 19 - 15fx 

Optical Engineering Handbook, General Electric Co., Scranton, Pa., (1963). 

One hundred-and-eighteen-minute is the longest-lived radioisotope of fluorine and may be produced by one of three nuclear reactions  

The most generally accessible machine is the nuclear reactor, and large activities of F can be induced by the neutron bombardment of oxygen salts of lithium [reaction (3)]. Lithium carbonate is the most convenient oxygen salt because of its high thermal stability (temperatures around 250° are developed by self-heating of lithium salts in an intense neutron flux), its ease of purification (since lithium carbonate has a negative temperature coeflScient of solu- 

The recommended procedure yields NaF solutions of known chemical composition, from which other inorganic F compounds may be synthesized either by direct chemical methods or by isotopic exchange. The use of apparatus of polyethylene (or other comparable plastics) is recommended for most parts of the preparation, first to reduce contaminants in the target material and second to reduce losses of HF in the final purification stage. 

Fifteen grams of analytical-grade lithium carbonate is dissolved in 1 1. of double-distilled water in a polyethylene beaker. The solution is first boiled on a steam bath and the beaker is then placed in an oven at 100° to allow the lithium carbonate crystals to settle. As much as possible of the hot supernatant solution is decanted and the remaining wet crystals are dried at 100°. Approximately 8 g. of recrystallized lithium carbonate is obtained. 

A standard aluminum irradiation can (e.g., 1.2-cm. radius, 5-cm. length) is fitted with an aluminum liner tube (e.g., 0.9-cm. radius, 5-cm. length) to provide a 3-mm. annulus into which lithium carbonate can be packed, f Depending on the amount of F required (see below for the expected yield of F per gram) up to 10 g. of recrystallized lithium carbonate is packed into the annular space within 

---

It may be mentioned that diazonium fluoborates containing the nitro group usually decompose suddenly and with violence upon heating, hence if o- or p-fluonitrobenzene are required, the fluoborates (in 10-20 g. quantities) should he mixed with 3-4 times their weight of pure dry sand (or barium sulphate or sodium fluoride) and heated cautiously until decomposition commences intermittent heating will be required to complete the reaction. 

Writing the equation in the usual way directs too much attention to the atoms and not enough to the electrons We can remedy that by deleting any spec tator ions and by showing the unshared electron pairs and covalent bonds that are made and broken Both sodium hydroxide and sodium fluoride are com pletely ionized in water therefore Na" which ap pears on both sides of the equation is a spectator ion Hydrogen fluoride is a weak acid and exists as undissociated HF molecules in water... 

Valentinite, see Antimony(III) oxide Verdigris, see Copper acetate hydrate Vermillion, see Mercury(II) sulflde Villiaumite, see Sodium fluoride Vitamin B3, see Calcium (+)pantothenate Washing soda, see Sodium carbonate 10-water Whitlockite, see Calcium phosphate Willemite, see Zinc silicate(4—)... 

Cryolite. Cryohte constitutes an important raw material for aluminum manufacturing. The natural mineral is accurately depicted as 3NaF AIF., but synthetic cryohte is often deficient in sodium fluoride. Physical properties are given in Table 4. 

There are several processes available for the manufacture of cryoHte. The choice is mainly dictated by the cost and quaUty of the available sources of soda, alumina, and fluoriae. Starting materials iaclude sodium aluminate from Bayer s alumina process hydrogen fluoride from kiln gases or aqueous hydrofluoric acid sodium fluoride ammonium bifluoride, fluorosiUcic acid, fluoroboric acid, sodium fluosiUcate, and aluminum fluorosiUcate aluminum oxide, aluminum sulfate, aluminum chloride, alumina hydrate and sodium hydroxide, sodium carbonate, sodium chloride, and sodium aluminate. 

The use of CIF and BrF as ionizing solvents has been studied (102,103). At 100°C and elevated pressures, significant yields of KCIF [19195-69-8] CsClF [15321-04-7], RbClF [15321-10-5], I-CBrF [32312-224], RbBrF [32312-224], and CsBrF [26222-924]obtained. Chlorine trifluoride showed no reaction with lithium fluoride or sodium fluoride. 

Most A1F. and cryoHte producers have their own HF production faciUties. HF vapor is reacted with alumina trihydrate to form A1F. in a fluid-bed reactor. HF is reacted with sodium hydroxide to form sodium fluoride, which is then used to produce cryoHte. Producers who manufacture these products solely for use in the aluminum industry do not generally install Hquid HF storage and handling faciHties, and do not participate in the merchant HF market. 

The monofluorophosphates can be prepared by neutralization of monofluorophosphoric acid (1). Sodium monofluorophosphate [7631 -97-2] is prepared commercially (57) by fusion of sodium fluoride and sodium metaphosphate, and the potassium monofluorophosphate [14104-28-0] can be prepared similarly. Insoluble monofluorophosphates can be readily prepared from reaction of nitrate or chloride solutions with sodium monofluorophosphate. Some salts are prepared by metathetical reactions between silver monofluorophosphate [66904-72-1] and metal chlorides. 

The JnitedSfates Pharmacopeia (76) specifications for sodium monofluorophosphate require a minimum of 12.1% fluoride as PO F (theoretical 13.2%) and a maximum of 1.2% fluoride ion reflecting unreacted sodium fluoride. Analysis for PO F is by difference between total fluoride ia the product less fluoride ion as determined by a specific ion electrode. The oral LD q of sodium monofluorophosphate ia rats is 888 mg/kg. 

Sodium has two fluorides, sodium fluoride [7722-88-5] and sodium bifluoride [1333-83-1]. 

Sodium fluoride is normally manufactured by the reaction of hydrofluoric acid and soda ash (sodium carbonate), or caustic soda (sodium hydroxide). Control of pH is essential and proper agitation necessary to obtain the desired crystal size. The crystals are centrifuged, dried, sized, and packaged. Reactors are usually constmcted of carbon brick and lead-lined steel, with process lines of stainless, plastic or plastic-lined steel diaphragm, plug cock, or butterfly valves are preferred. 

Both sodium fluoride and sodium bifluoride are poisonous if taken internally. Dust inhalation and skin or eye contact may cause irritation of the skin, eyes, or respiratory tract, and should be avoided by the use of proper protective equipment (1). 

Fluoridation of potable water suppHes for the prevention of dental caries is one of the principal uses for sodium fluoride (see Water, municipal WATER treatment). Use rate for this appHcation is on the order of 0.7 to 1.0 mg/L of water as fluoride or 1.5 to 2.2 mg/L as NaF (2). NaF is also appHed topically to teeth as a 2% solution (see Dentifrices). Other uses are as a flux for deoxidiziag (degassiag) rimmed steel (qv), and ia the resmelting of aluminum. NaF is also used ia the manufacture of vitreous enamels, ia pickling stainless steel, ia wood preservation compounds, caseia glues, ia the manufacture of coated papers, ia heat-treating salts, and as a component of laundry sours. 

The same reactants are used for manufacture as for sodium fluoride. An excess of acid is required to crystallize the bifluoride. The crystals are dewatered, dried, sized, and packaged. Cooling of the reaction is necessary to avoid over-heating and decomposition. Reactors and auxiUary equipment are the same as for sodium fluoride. 

Sodium fluorosulfate may be prepared by the action of fluorosulfuric acid on powdered, ignited sodium chloride (13) or of sulfur trioxide on sodium fluoride (48). In general, the alkah metal fluorosulfates may be prepared from the ammonium salt by evaporating a solution containing that salt and an alkah metal hydroxide (77). The solubiUties of some Group 1 and 2 fluorosulfates in fluorosulfuric acid have been deterrnined (93). 

Direct Fluorination. This is a more recently developed method for the synthesis of perfluorinated compounds. In this process, fluorine gas is passed through a solution or suspension of the reactant in a nonreactive solvent such as trichlorotrifluoroethane (CFC-113). Sodium fluoride may also be present in the reaction medium to remove the coproduct hydrogen fluoride. There has been enormous interest in this area since the early 1980s resulting in numerous journal pubHcations and patents (7—9) (see Fluorine compounds, organic-direct fluorination). Direct fluorination is especially useful for the preparation of perfluoroethers. 

Chloro-2,4,6-trifluoropyrimidine [697-83-6] has gained commercial importance for the production of fiber-reactive dyes (465,466). It can be manufactured by partial fluoriaation of 2,3,5,6-tetrachloropyrimidine [1780-40-1] with anhydrous hydrogen fluoride (autoclave or vapor phase) (467) or sodium fluoride (autoclave, 300°C) (468). 5-Chloro-2,4,6-trifluoropyrimidine is condensed with amine chromophores to provide the... 

The standard potential for the anodic reaction is 1.19 V, close to that of 1.228 V for water oxidation. In order to minimize the oxygen production from water oxidation, the cell is operated at a high potential that requires either platinum-coated or lead dioxide anodes. Various mechanisms have been proposed for the formation of perchlorates at the anode, including the discharge of chlorate ion to chlorate radical (87—89), the formation of active oxygen and subsequent formation of perchlorate (90), and the mass-transfer-controUed reaction of chlorate with adsorbed oxygen at the anode (91—93). Sodium dichromate is added to the electrolyte ia platinum anode cells to inhibit the reduction of perchlorates at the cathode. Sodium fluoride is used in the lead dioxide anode cells to improve current efficiency. 

---