タイトルまたは説明

Synthetic Cryolite Na3AlF6 & Sodium Fluoroaluminate  Artificial Cryolite 

 How to produce Cryolite

Cryolite is the main constituent of the electrolyte used in alumina electrolysis. Chemically it is Na3AlF6, a double fluoride of sodium and aluminium. It is a white granular powder. Certain impurities may give it a grey or pink discoloration. The freezing point of cryolite is ***9°C.

Synthetic Cryolite is made from fluorspar (CaF2), which is found as a natural mineral. Fluorspar is treated with sulphuric acid to produce hydrofluoric acid HF.

CaF2 +H2SO4 = 2HF (g) +CaSO4 (s) (3)

HF is then reacted with sodium oxide Na2O and alumina to produce cryolite.

Cryolite ratio= Molar Ratio of NaF

Molar Ratio of Alf3

1. Physical and chemical properties of synthetic cryolite:

The product is a white crystalline powder or a sandy-size granularity, and a pinkish crystalline powder or a sandy-size granularity as well. Sp.gr.2.*5—3.*5g/cm3, melting point about ***5°C, specific heat 1.**6j/g°C at *8—**0°C. Its slightly soluble in water, but insoluble in anhydrous hydrogen fluoride. The content of its crystal water will be decreased while the increasing of the molecular ratio, therefore its loss on ignition will be also decreased while the increasing of the molecular ratio. After the paste of synthetic cryolite with different molecular ratio dehydrates, the loss on ignition at **0°C will appear *0.*4%, 6.*2% and 2.*6% when the molecular ratio reaches 1.*4, 2.*4 and 2.*3 reactively.

   
2. Applications: 
Metal surface treatment: As component in pickling pastes for stainless steel. 
Production of abrasives: As active filler in resinbonded adrasives for metal treatment. 
Production of enamel, glazing frits and glass: As abrasives, opacifying agent. 
Production of soildering agent: Component for fluxing agent. 
Production of welding agent: Component of weilding rod coatings and welding powders. 
Aluminum-metallurgy: As component of fluxing agents, protective and refining salts

3. Specification :