URANIUM. 155 



From all of these figures we may calculate the molecular 

 weight of the uraiiic acetate as follows : 



From percentage of {J■fi^ C2H3(UO)02.H20 = 212.629, ± .242 



CO2 " = 212.999, ± -476 



H2O " = 211.184, zi= 1.863 



General mean " ^ 212.685, zb .214 



We have now before us the molecular weights of four 

 uranium compounds, giving us four values for U : 



(i.) UO = 134.652, d= .097 Ebelmen. 



(2.) Na^U^Oj = 634.S65, ±: .191 Wertheim. 



vJ- 



UgO^ = 423-342, zh .451 Peligot. 



(4.) C,H3(UO)02.H.p = 212.685, ± -214 - " 



The four values for uranium combine as follows : 



From (i) U = 118.6S9, i .097 Ebelmen. 



" (2) " = 119.2S2, d= .048 Wertheim. 



" (3) " ^ 119.830, dr .150 Peligot. 



" (4) " = 119.885,^.215 



General mean '• = 1 19.241, ±: .041 



Or, if = 10, U = 119.515, or 239.030. 



Considering Peligot's figures by themselves, and combin- 

 ing values 3 and 4, we have U = 119.849, ± .123 ; or, if 

 O = 10, U = 120.125, or 240.250. 



It is plain that the atomic weight of uranium needs to be 

 scrupulously revised. The foregoing figures are by no 

 means satisfactory. Chemically considered, it is probable 

 that Peligot's work is the best, and that his results should 

 be given preference. His figures from the oxalate and the 

 acetate tally well with each other, whereas Ebelmen's two 

 sets of results vary Avidely. From the percentage of UO 

 yielded by the oxalate, Ebelmen's figures give a low value 

 for U. From his oxidation of UO to V^O^ we get a value 

 nearly two units higher. Peligot, in his work with the 

 oxalate, found it, even after three or four crystallizations, 

 to be contaminated with oxalic acid, and rejected the figures 

 obtained from impure material. Probably Ebelmen's low 

 values are due to the same impurity. 



