Tungsten is extracted from the mineral scheelite (CaWO4) by roasting it with natrite (Na2CO3) at a temperature of about 700 °C. This converts the CaWO4 to water soluble sodium tungstate (NazWO4). The solid product from the roaster (called "calcine") is transferred to a leacher. In the leacher chilled water is added to dissolve the NazWO4. The chilled water dissolves only the NazWO4 in the solid calcine. The scheelite that enters the roast is mixed with gypsum (CaSO4-2H2O). This stream is 85.2%w CaWO4 and 14.8%w CaSO4-2H2O. (%w means “percent-by-weight.") Four reactions take place during this process. In the roaster: 1: CaWO4 + Na2CO3 - NazWO4 + CaO + CO2 2: CaSO4•2H2O – CaSO4 + 2H2O In the leacher:

Tungsten is extracted from the mineral scheelite (CaWO4) by roasting it with natrite (Na2CO3) at a temperature of about 700 °C. This converts the CaWO4 to water soluble sodium tungstate (NazWO4). The solid product from the roaster (called "calcine") is transferred to a leacher. In the leacher chilled water is added to dissolve the NazWO4. The chilled water dissolves only the NazWO4 in the solid calcine. The scheelite that enters the roast is mixed with gypsum (CaSO4-2H2O). This stream is 85.2%w CaWO4 and 14.8%w CaSO4-2H2O. (%w means “percent-by-weight.") Four reactions take place during this process. In the roaster: 1: CaWO4 + Na2CO3 - NazWO4 + CaO + CO2 2: CaSO4•2H2O – CaSO4 + 2H2O In the leacher:

Principles of Modern Chemistry

8th Edition

ISBN:9781305079113

Author:David W. Oxtoby, H. Pat Gillis, Laurie J. Butler

Publisher:David W. Oxtoby, H. Pat Gillis, Laurie J. Butler

Chapter17: Electrochemistry

Section: Chapter Questions

Problem 80AP

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