URANIUM. 267 



Zimmerrnann's second method was essentially that of Wertheim, 

 namely, the ignition of the double acetate UO 2 (C 2 H 3 2 ) 2 .NaC 2 H 3 2 , the 

 residue being sodium uranate, Na 2 U 2 7 . 



Double Acetate. Uranate. Per cent. Uranate. 



4.272984 2.886696 67.557 



5.272094 3-560770 67.540 



2.912283 1.967428 67.556 



2.149309 67.555 



Mean, 67.552, dz .0027 

 Wertheim found, 67.523, dz .0076 



General mean, 67.549, dz .0025 



All the data for uranium now sum up thus : 



(i.) Per cent. UO 2 from uranyl oxalate, 71.782, dz .019 



(2.) 6C0 2 : U 3 8 : : 100 : 321.443, dz .338 



(3.) Molecular weight of uranyl acetate, 423.842, .4222 



(4.) 3UO 2 : U 3 O 8 : : 100 : 103.9276, dz .0003 



(5.) Per cent. Na 2 U 2 O 7 from UO 2 .Na(C 2 H 3 O 2 ) 3 , 67.549, dz .0025 



Computing with = 15.879, .0003 ; C = 11.920, .0004, and Na = 

 22.881, .0046, we have 



From (I) = 235.948, dz .1938 



From (2) ; . " = 238.462, dz .2953 



From (3) " =238.541, dz-4223 



From (4) " = 237.770, dz .0055 



From (5) " = 237.902, dz .0283 



General mean ... U = 2 37-774, 4= .0054 



If = 16, U = 239.586. 



In this case Zimmermann's data control the final result. All the other 

 determinations might be rejected without appreciable effect. 



