266 THE ATOMIC WEIGHTS. 



weights of dioxide, with C = 12 and O = 16, 1 have added a third column, 



in which the carbon percentages are converted into percentages of C0 2 : 



H.,0. C. CO* 



21.60 11.27 4 J .323 



21. 16 11.30 41-433 



21.10 11.30 41-433 



2 1. 2O II.IO 4O.7OO 



Mean, 21.265, .187 Mean, 11.24 Mean, 41.222, zh .092 



From these data we get the following values for the molecular weight 

 of uranyl acetate : 



From percentage of U 3 O 8 423.183, .4781 



From percentage of CO 2 423.842, =b .9462 



From percentage of H 2 O : 420.386, dr 2.9033 



General mean 423.257, =h .4222 



In the posthumous paper of Zimmermann. edited by Kriiss and Alibe- 

 goff,* the atomic weight of uranium is determined by two methods. 

 First, U0 2 , prepared by several methods, is converted into U 3 O 8 by heat- 

 ing in oxygen. To begin with, U 3 8 was prepared, and reduced to U0 2 

 by ignition in hydrogen. When the reduction takes place at moderate 

 temperatures, the U0 2 is somewhat pyrophoric, but if the operation is 

 performed over the blast lamp this difficulty is avoided. After weighing 

 the UO 2 , the oxidation is effected, and the gain in weight observed. The 

 preliminary U 3 O 8 was derived from the following sources : A, from ura- 

 nium tetroxide ; B, from the oxalate ; C, from uranyl nitrate ; D, by 

 precipitation with mercuric oxide. l"he full data, lettered as indicated 

 above, are subjoined : 



UO^, U- A O%. Per cent, of Gain. 



8.9363 9.2872 3-927 



7.9659 8.2789 3.929 



12.4385 12.9270 3.927 



f 12.8855 i3-39'3 3.925 



B. -j 5.7089 5.9331 3.927 



( 9.6270 10.0051 3.928 



13.1855 13-7036 3-929 



9.9973 10.3901 3.929 



15.8996 16.5242 3.928 



7-4326 7.7245 3.927 



Mean, 3.9276, .0003 

 Ebelmen found, 3.913, d= .009 



General mean, 3.9276, .0003 



Iii short, Ebelmen's mean vanishes when combined with Zimmer 

 lann's. 



* Ann. d. Chern., 232, 299. 1886. 



