172 PROCEEDINGS OF THE AMERICAN ACADEMY. 



interchanged in publication, as Brauner has suggested, for the lower 

 value 140.8 was assigned to neodymium. 



Next Brauner, 3 in 1898, starting with material purified by Shapleigh 

 by crystallization of the double ammonium nitrate, continued the 

 process of crystallizing this salt until neodymium was completely 

 eliminated, then removed a trace of lanthanum by fusion with potas- 

 sium nitrate, extraction of the praseodymium oxide with ammonium 

 nitrate, and fractionation with ammonia and oxalic acid. By both 

 the analysis of the oxalate and synthesis of the sulphate thirteen 

 results were obtained between 140.84 and 141.19, with an average of 

 140.95. 



Jones, 4 in the same year, further purified double ammonium nitrate 

 furnished by the Welsbach Light Company by crystallization until 

 the neodymium content was about 0.06 percent, as determined by 

 comparison with neodymium solutions of known concentration. 

 Cerium was removed by the basic nitrate process, and traces of lan- 

 thanum by further crystallization of the double ammonium nitrate. 

 Spectroscopically only a trace of lanthanum and no cerium could be 

 detected. The oxalate was converted to trioxide by ignition in air 

 and then in hydrogen, and after being weighed the oxide was converted 

 to sulphate. Twelve determinations between 140.38 and 140.54 

 give an average of 140.46. 



Scheele 5 also purified material first by crystallization of the double 

 ammonium nitrate, next by extracting the black oxide with ammonium 

 nitrate, and then by precipitation of the oxalate. In a final series of 

 determinations oxalate was converted to trioxide in a current of 

 hydrogen, and the oxide in turn to sulphate. From the ratio of tri- 

 oxide to sulphate five values between 140.48 and 140.61 resulted. 



In 1901 Brauner 6 confirmed his earlier work by four different 

 methods, using similarly purified material. By igniting weighed 

 quantities of octahydrated sulphate to the black oxide and correcting 

 for the oxidizing power of the oxide as determined iodimetrically, he 

 obtained from the ratio Pr 2 3 : P^SO^ 8 H 2 two results, 141.13 

 and 141.04. Weighed amounts of carefully dehydrated sulphate 

 were then converted to oxide in the same way, yielding the values 

 140.96 and 140.94. Air-dried oxalate was weighed and ignited, and 



3 Proc. Chem. Soc, (1898) 70. 



4 Am. Chem. Jour., 20, 345 (1898). 



5 Zeit. anorg. Chem., 17, 310 (1898). 



6 Proc. Chem. Soc. (1901) 65; Abegg, Handb. d. anorg. Chem., 3 (1) 263 

 (1906). 



