Peroxy compounds, of hafnium and zirconium

Periodates, 1 168 analysis of, 1 170 Periodic acid (EblOs), 1 172 solubility in nitric acid, 1 173 Peroxy compounds, of hafnium and zirconium, 3 72... 

In order to proceed with the fractionation, the zirconium hafnium phosphates must be converted into acid-soluble compounds. Digestion of the moist phosphates with a mixture of sodium hydroxide and sodium peroxide yields a dense white peroxy compound, which can be washed free from the soluble phosphates, and which is soluble in acid with the evolution of oxygen. This reaction is utilized in the following procedure, except that 30 per cent hydrogen peroxide has been substituted for the sodium peroxide. 

To prepare low-hafnium zirconia, the mother liquor from the first fractional precipitation is treated with ammonium hydroxide to precipitate the hydroxides, which are then filtered and redissolved in a calculated amount of moderately concentrated sulfuric acid. This solution is then diluted with the amount of water required to give 2 N sulfuric acid solution that contains 5 per cent RO2. From a fraction containing 0.7 per cent hafnium, one fractionation in which about 60 per cent of the total oxide is precipitated as the phosphate will yield a product containing only 0.2 per cent hafnium. Additional fractionations of the mother liquor will reduce the hafnium content to a concentration below the sensitivity of the arc spectrographic method used (about 0.05 per cent Hf). Because the impurities concentrate in the most soluble fraction, a complete phosphate precipitation is made on the final solution, the precipitate is washed with 2 N sulfuric acid, and then converted to the peroxy compound. For final purification, the acid-soluble peroxy compound is dissolved in hydrochloric acid, and the oxychloride prepared according to the procedure of Young and Arch. The oxychloride may then be used as a starting material for the preparation of any other zirconium compound. 

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