The Preparation of Low-hafnium Zirconia

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. 

Inorganic Syntheses, Volume III Edited by Ludwig F. Audrieth 1950 by McGraw-Hill Book Company, Inc. 

Cyanamide, synthesis 9 Dicyanodiamide, synthesis 10 Barium thiocyanate, synthesis 5 Potassium ootacyanomolybdate (IV) 2-hydrate, synthesis 43 Zirconium hafnium phosphates, synthesis IOC 

The method described below represents a modification Stran Hall Research Laboratory, New York, N.Y. t UniveiBity of Illinois, Urbana, Rl. 

The apparatus for the preparation of nitrogen (V) oxide is shown in Fig. 18. Oxygen is bubbled into bottle A con- 

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