76 



Dr. G. H. Bailey. 



[May 9, 



times. On precipitation of the final products with ammonia the 

 crude zirconia is obtained, which forms the starting point for further 

 purification. In farther operations, reagents (such as potassium or 

 sodium salts) which could not be removed by volatilisation were 

 avoided, and even at the present stage it was considered advisable to 

 redissolve the zirconia in hydrochloric acid, and reprecipitate with 

 ammonia three times in order to get rid of the bulk of the sodium 

 salts. 



Purification of the Crude Zirconia. 



This crude zirconia, free from the impurities that occur in larger 

 quantity, was dissolved in hydrochloric acid, and crystallised out as 

 oxychloride. The aqueous solution of this, slightly acidulated, was 

 treated with sulphuretted hydrogen for twenty-four hours ; a gela- 

 tinous precipitate was obtained of a purplish-black colour, consisting 

 principally of sulphides of silver and copper, together with some 

 hydrated zirconia. To the filtrate saturated with sulphuretted 

 hydrogen was now added a little ammonia, which had the effect of 

 bringing down a little more zirconia, and also the small quantities of 

 impurities precipitable by ammonium sulphide. The liquid was now 

 acidulated and boiled down to get rid of the sulphuretted hydrogen , 

 and excess of oxalic acid added to the concentrated solution to pre- 

 cipitate gadolinite earths, and finally treated with ammonium oxalate. 

 There still remained some iron which had either not been removed or 

 had been introduced in the course of treatment. To separate this 

 the oxychloride was crystallised repeatedly from concentrated hydro- 

 chloric acid, and finally washed with a mixture of the acid with 

 one part of alcohol and ten parts of ether. The only impurity 

 that could now be detected was soda, which the zirconia retained 

 with the greatest tenacity. 



This was removed by precipitating the zirconia several times by 

 means of ammonia, and redissolving it in hydrochloric acid. The 

 zirconia finally precipitated by ammonia was washed* so long as any 

 ammonium salts could be detected in the wash water. 



The zirconia obtained was tested as to purity in the following 

 way:— 



(1.) A portion treated with hydrofluoric acid showed no alteration 

 in weight ; 



(2.) The moist oxide dissolved completely in oxalic acid ; 



(3.) On ignition it was perfectly white (inclined to a bluish cast), 

 and a quantity exhausted with hydrochloric showed no trace of iron 

 by the most delicate tests. 



* Some of tlie earlier results had to be rejected because of incomplete washing. 

 20 grams of zirconia required to be washed 150 times at the pump before ammonia 

 salts were got rid of, at least 50 litres of water being used in the process. 



