cryolite

Description

Cryolite is an uncommon mineral salt of sodium, fluoride and aluminum that was first discovered on the west coast of Greenland. The supply was depleted by 1987, and synthetic cryolite is now produced from the common mineral fluorite. Cryolite is used at very high application rates of 5-30 kg/ha to control Lepidoptera and Coleoptera on certain fruits, vegetables and citrus. 92% of total cryolite applied in the U.S. is used on grapes in California.

Chemical Properties

Sodium aluminum fluoride is a snow-white crystalline solid, powder or vitreous mass. The crystalline solid (natural product (cryolite) may be colored reddish or brown or even black but loses this discoloration on heating); synthetic product is an amorphous powder. Odorless

Physical properties

Habit: massive, granular, pseudocubic euhedral crystals.
Color: snow white, gray, reddish white, or brownish white.
Diaphaneity: transparent to translucent.
Luster: vitreous, greasy.
Streak: white.
Cleavage: [001], [110], [101].
Fracture: uneven.
Occurrence: large bed in a granitic vein in gray gneiss.
Melting point: 1009°C.

Uses

Electrolyte in the reduction of alumina to aluminum; ceramics; insecticide; binder for abrasives; electric insulation; explosives; polishes.

Uses

Cryolite is commonly used as an electrolyte for aluminum electrolysis. Alumina is dissolved in molten cryolite is used to dissolve alumina during aluminium processing.

Definition

A natural fluoride of sodium and aluminum or made synthetically from fluorspar, sulfuric acid, hydrated alumina, and sodium carbonate.

General Description

An odorless white solid or powder. Mp: 1291°C. Density: 2.95 g cm-3. Dust irritates the eyes and skin; inhaled dust irriates the nose, mouth and lungs. Insoluble in water. Synthesized by fusion of sodium fluoride and aluminum fluoride as a electrolyte in the reduction of alumina to aluminum metal. Occurs in nature as the mineral cryolite. Aqueous suspensions of powdered sodium aluminum fluoride are used as insecticides.

Reactivity Profile

SODIUM ALUMINUM FLUORIDE is non-combustible. Emits toxic fumes when heated to decomposition. Incompatible with strong oxidizing agents and strong acids. Decomposed by bases, which can generate soluble fluorides. Soluble in concentrated sulfuric acid.

reaction suitability

core: aluminum
reagent type: catalyst

Agricultural Uses

Insecticide: Sodium aluminum fluoride is used as an insecticide on food crops and ornamentals, and also in aluminum refining and making ceramics, glass and polishes. Cryolite is used to control a variety of pests on cucurbits (melons, cantaloupe, water melon, pumpkins, all types of squash), fruiting vegetables (eggplant, pepper, broccoli, Brussels sprouts, cabbage, cauliflower, collards, head and leaf lettuce, kohlrabi), kiwi (in California only), pears, radish, cranberry and peaches, grapefruit, lemon, lime, orange, tangelo, tangerines, tomatoes, apples, potatoes, beans and grapes. Also on ornamental plants, woody shrubs and vines. Not listed for use in EU countries. Registered for use in the U.S

Trade name

KRYOCIDE®; CHIOLITE®; CRYOLITE 93®; ICE-SPAR®; ICETONE®; KOYOSIDE®; KRIOLIT®; PROKIL® Sodium aluminum fluoride; VILLIAUMITE®

Safety Profile

Poison by ingestion. Used as a pesticide. Mutation data reported.When heated to decomposition it emits toxic fumes of Fand NazO. See also FLUORIDES.

Synthesis

A method for producing cryolite (sodium fluoroaluminate), which comprises the steps of:

1, anhydrous hydrofluoric acid is added to water, and dissolved to generate hydrofluoric acid with a mass fraction of 40% at room temperature and under normal pressure for backup;

2, at room temperature and pressure, aluminum hydroxide and sodium hydroxide will be added to the reaction tank in proportion to the stirring reaction to generate sodium meta-aluminate;

3. 40% hydrofluoric acid reserved in step 1 is added to the reaction tank in step 2 to react with sodium meta-aluminate to generate crude product;

4. The crude product is precipitated, centrifuged, separated, washed, dried and processed to obtain the finished product sodium fluoroaluminate.

Potential Exposure

Sodium aluminum fluoride is used in making pesticides, ceramics, glass, and polishes; in refining reduction of aluminum, flux, glass, and enamel.

Shipping

UN3077 Environmentally hazardous substances, solid, n.o.s., Hazard class: 9; Labels: 9-Miscellaneous hazardous material, Technical Name Required.

Incompatibilities

Incompatible with strong acids such as sulfuric, strong oxidizers, hydrogen fluoride.

Toxics Screening Level

The initial threshold screening level (ITSL) for sodium aluminum fluoride (Na3AlF6 ) is 270μg/m3 based on a 8 hour averaging time.

Waste Disposal

In accordance with 40CFR 165 recommendations for the disposal of pesticides and pesticide containers. Must be disposed properly by following package label directions or by contacting your local or federal environmental control agency, or by contacting your regional EPA office.