342 



CARNEGIE INSTITUTION OF WASHINGTON. 



means of the absorption spectrum, to detect with ease 0.05 per cent of 

 neodymium in praseodymium material. In some of the fractions the 

 cerium content was at least as low, although others were found to 

 contain perceptible quantities of the latter element. The presence of 

 cerium is, however, less serious than the presence of neodymium, since 

 the atomic weight of cerium lies far nearer that of praseodymium than 

 does the atomic weight of neodymium. 



Series II. 



PrCl3:3AgCl 



Fraction. 



3474. 

 3474. 

 3474. 

 3474 . 



Average . 



4383. 

 4383. 



Average. 



4381. 

 4381. 



Average . 



4379. 

 4379. 



Average . 



4374. 

 4374. 

 4374. 

 4374. 

 4374. 



Average. 



4371. 

 4371. 



Average. 



4368. 

 4368. 



Average. 



Corrected 

 weight of 

 PrCla in 

 vacuum. 



Corrected 

 weight of 

 AgCl in 

 vacuum. 



grams. prams. 



4.12851 7.17915 



6.91605 1 12.02520 



7.66554 13.32936 

 5.01155 I 8.71348 



Ratio 

 PrCl3:3AgCl 



6.04235 

 6 . 14745 



6.32550 

 4.59463 



10.50735 

 10 . 69042 



10.99847 

 7.98909 



5.96661 

 6.87536 



6 . 85492 

 8.01711 

 6.17044 

 6.90040 

 7.08498 



6.20845 

 7.07595 



5.77646 

 5 . 72002 



10.37533 

 11.95497 



11.91764 

 13.93942 

 10.72822 

 11.99853 

 12.32003 



10.79543 

 12.30384 



10.04393 

 9.94637 



Average of Series I 



Average of Series II 



Average of Series I and II . 



0.575070 

 0.575130 

 0.575088 

 0.575141 



0.575107 



. 575059 

 0.575041 



0.575050 



0.575122 

 0.575111 



Atomic 

 weight of 



praseo- 

 dymium. 



0.575117 



. 575073 

 0.575102 



. 575088 



0.575190 

 0.575139 

 0.575154 

 0.575102 

 0.575079 



0.575133 



0.575100 

 0.575100 



0.575100 



0.575119 

 0.575081 



0.575100 



140.915 

 140.941 

 140.922 

 140.950 



140.932 



140.911 

 140.904 



140.908 



140.939 

 140.934 



140.936 



140.918 

 140.930 



140.924 



140.967 

 140.945 

 140.954 

 140.930 

 140.919 



140.943 



140.928 

 140.928 



140.928 



140.937 

 140.921 



140.929 



140.918 

 140.933 

 140.925 



