ATOMIC WEIGHTS 375 



71.794 103.900 



71.793 



71.778 



71.790 103.930 



Mean, 71.782, ± .019 Mean, 103.913, ± .009 



Hence U = 337.70. Hence U = 240.?5. 



Wertheim's ' experiments were even simpler in character than those 

 of Ebehnen. Sodio-uranic acetate, carefully dried at 200°, was ignited, 

 leaving the following percentages of sodium uranate : 



67.51508 

 67.54558 

 67.50927 



Mean, G7.52331, ± .0076 



Hence .U= 239.29. 



The final results of Peligot's " investigations appeared in 1846. Both 

 the oxalate and the acetate of uranium were studied and subjected to 

 combustion analysis. The oxalate was scrupulously purified by repeated 

 crystallizations, and thirteen analyses, representing different fractions, 

 were made. Seven of these gave imperfect results, due to incomplete 

 purification of the material; six only, from the later crystallizations, 

 need to be considered. In these the lu'anium was weighed as UgOg, and 

 the carbon as COo. From the ratio between the CO, and UgOg the atomic 

 weight of uranium may be calculated without involving any error due 

 to traces of moisture possibly present in the oxalate. I subjoin Peligot's 

 weighings, and give, in the third column, the UgOg proportional to 100 

 parts of COo : 



CO.. 



1.456 

 1.369 

 2.209 

 1.019 

 1.069 

 1.052 



.338 



Hence U = 240.23. 



iJourn. prakt. Chem., 29, 209. 1843. 

 ^Compt. Rend., 22, 487. 1846. 



