The thermal decomposition of nickel and zinc fluoride tetrahydrates

Nickel fluoride tetrahydrate, NiF2·4H2O, decomposes in three steps when heated, the products depending on the atmosphere in which the decomposition occurs. In dry air or in dry argon three moles of water are lost at about 125°, and the monohydrate, NiF2·H2O, is formed. At about 225°, the monohydrate loses water and hydrogen fluoride, and NiOHF·3NiF2 is formed. The latter compound loses an additional mole of hydrogen flouride at about 430°, and the final product is a mixture of nickel fluoride and nickel oxide in a 3:1 mole ratio. In the presence of water vapour the final decomposition product is solely nickel oxide; the other steps are the same. Zinc fluoride tetrahydrate loses four moles of water at temperatures above about 75°, forming anhydrous zinc fluoride.