26G 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 COj : 



H.fi. C. CO^. 



21.60 11.27 41-323 



21.16 . 11.30 41433 



21.10 11.30 41.433 



21.20 11.10 40.700 



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



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

 of uranyl acetate : 



From percentage of UgOg 423.183, d= .4781 



From percentage of COj 423.842, i .9462 



From percentage of H^O 420.386, it 2.9033 



General mean 423.257, ± .4222 



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

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

 First, UO^, prepared by several methods, is converted into UgOg by heat- 

 ing in oxygen. To begin with, UgOg was prepared, and reduced to UOj 

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

 temperatures, the UO.^ is somewhat pyrophoric, but if the operation is 

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

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

 preliminary UjOg was derived from the following sources : A, from ura- 

 nium tetroxide ; B, from the oxalate ; C, from uran}^ nitrate ; D, by 

 precipitation with mercuric oxide. The full data, lettered as indicated 

 above, are subjoined : 



UO^. U-iO^. Per cent, of Gain. 



8.9363 9.2872 3.927 



A. \ 7.9659 8.2789 3.929 

 12.4385 12.9270 3.927 

 12.8855 i3-39'3 3-925 



B. \ 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 



{t 



4326 7-7245 3.927 



Mean, 3.9276, ± .0003 

 Ebelmen found, 3.913, ± .009 



General mean, 3.9276, zh .0003 



In sliort, Ebelmen's mean vanishes when combined witli Zimmer' 

 mann's. 



» Ann. d. Chem., 232, 299. 1886. 



