Nickeldifluorid

synthetischeNickel fluoride tetrahydrate [13940-83-5], NiF2.4H2O, and its anhydrous counterpart, nickel fluoride [10028-18-9], NiF2 , are the only known stable binary compounds of nickel and fluorine. The former is a greenish light yellow crystal or powder prepared by the addition of nickel carbonate to 30-50% aqueous HF solution. The nickel fluoride formed first goes into solution and then precipitates out as the tetrahydrate as the concentration of Nickel fluoride increases and that of HF decreases. When the addition of nickel is complete, the solution and the precipitates are dried at 75-100°C until all the water is expelled. The tetrahydrate has high solubility in aqueous HF, eg, 13.3 wt % in 30% HF. It is slightly soluble in water and insoluble in alcohol and ether. Anhydrous Nickel fluoride, a light yellow colored powder, is prepared by the action of anhydrous HF on anhydrous NiCl2 , or nickel fluoride tetrahydrate at 300°C. It is also prepared by heating a mixture of NH4.HF2 and NiF2.4H2O. The other methods include the fluorination of metal salts using excess SF4 or using ClF3 at elevated temperatures, or the reaction of NiCO3 and anhydrous HF at 250°C.