FLUORIDE STANDARD Chemical Properties,Uses,Production
Of the general formula FyMx or MxFy, appear ance, odor and properties vary with specific compounds.
Any inorganic salt of hydrofluoric acid in which fluorine has a valence of ?1. Fluorides are major environmental pollutants released into the atmosphere
from aluminum reduction, steel manufacturing, and
coal-fired power plants. Fluoride pollution is assoc
Highly toxic; poison; mutagen; can cause
convulsions, changes in the respiratory system, liver
Small amounts of fluoride appear to be an essential nutrient. People in the United States ingest about 2 mg/day in water and food. A concentration of about 1 mg/L in drinking water effectively reduces dental caries without harmful effects on health. Dental fluorosis can result from exposure to concentrations above 2 mg/L in children up to about 8 years of age. In its mild form, fluorosis is characterized by white opaque mottled areas on tooth surfaces. Severe fluorosis causes brown to black stains and pitting. Although the matter is controversial, the EPA has determined that dental fluorosis is a cosmetic and not a toxic or an adverse health effect. Water hardness limits fluoride toxicity to humans and fish. The severity of fluorosis decreases in harder drinking water. Crippling skeletal fluorosis in adults requires the consumption of about 20 mg or more of fluoride per day over a 20-year period. No cases of crippling skeletal fluorosis have been observed in the United States from the longterm consumption of 2 L/day of water containing 4 mg/L of fluoride. The EPA has concluded that 0.12 mg/kg/day of fluoride is protective of crippling skeletal fluorosis. Fluoride therapy, where 20 mg/day is ingested for medical purposes, is sometimes used to strengthen bone, particularly spinal bones.
Fluorides are used as an electrolyte in
aluminum manufacture; a flux in smelting nickel, copper,
gold, and silver; as a catalyst for organic reactions, a wood
preservative; fluoridation agent for drinking water; a
bleaching agent for cane seats; in pesticides, rodenticides,
and as a fermentation inhibitor. They are utilized in the
manufacture of steel, iron, glass, ceramics, pottery, enam els, in the coagulation of latex; in coatings for welding
rods; and in cleaning graphite, metals, windows, and glass ware. Exposure to fluorides may also occur during prepara tion of fertilizer from phosphate rock by addition of
sulfuric acid. Air pollution by fluoride dusts and gases has
done substantial damage to vegetation and to animals in the
vicinity of industrial fluoride sources. However, the contri bution of ambient air to human fluoride intake is only a
few hundredths of a milligram per day, an amount that is
insignificant in comparison with other sources of fluoride.
Operations that introduce fluoride dusts and gases into the
atmosphere include: Grinding, drying, and calcining of
fluoride-containing minerals; acidulation of the minerals;
smelting; electrochemical reduction of metals with fluoride
fluxes or melts, as in the aluminum and steel industry; kiln firing of brick and other clay products and the combustion
Fluorides form explosive gases on con tact with strong acids or acid fumes.
Reaction of aqueous waste
with an excess of lime, followed by lagooning; and either
recovery or land disposal of the separated calcium fluoride.
FLUORIDE STANDARD Preparation Products And Raw materials