80 CHEMISTRY: BAXTER AND STEWART 
The Atomic Weight of Praseodymium — Continued 
FRACTION 
PrCls: 3Ag 
PrCla: 3AgCl 
AVERAGE VAIUES 
Average 
140.916 
140.931 
140.921 
4379 
140.910 
140.913 
4379 
140.915 
140.928 

Average 
140.913 
140.921 
140.917 
4377 
140.917 
4377 
140.917 
140.951 
Average 
140.917 
140.928 
4374 
140.916 
140 965 
4374 
140.916 
140.943 
4374 
140.959 
140.952 
4374 
140 . 926 
140.911 
4374 
140.911 
140.916 
4374 
140.911 
Average 
140.923 
140.937 
140.930 
4371 
140.915 
140.926 
4371 
140.922 
140.924 
Average 
140.919 
140.925 
140 . 923* 
4368 
140.916 
140.935 
4368 
140.922 
140.919 
Average 
140.919 
140.927 
140. 925 t 
Final Average 
140.923 
140.924 , 
* Increased by + 0.001 units to correct for cerium-content, 
t Increased hy + 0.002 units to correct for cerium-content. 
at 107.880. This result is not far from the value obtained by Brauner 
in both his researches, but is over three-tenths of a unit higher than the 
choice of the International Committee on Atom'c Weights. 
We are indebted particularly to the Carnegie Institution of Wash- 
ington for very generous assistance in carrying out this investigation,^ as 
well as to Dr. H. S. Miner of the Welsbach Light Company for the praseo- 
dymium material. 
1 Baxter and Chapin, Proc. Amer. Acad., 46, 213 (1911). 
2 The crystallization was begun by Mr. W. H. Whitcomb, continued by Messrs. B. W. 
Grimes and C. C. Wallace, and completed by O. J, Stewart. 
3 Richards, Proc. Amer. Acad., 32, 59 (1896). 
^This work will be described in detail before long in Proc. Amer. Acad. Arts Sci., 
Boston, and in /. Amer. Chem. Soc. 
