358 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 54 



Vandenberghe ' prepared molybdenum dibromide, wliicli was next re- 

 duced to metal by heating in hydrogen. The metal was then oxidized to 

 trioxide by means of nitric acid. The data are as follows: 



Mean, 66.692, ± .0015 



Corrected to a vacnnm this becomes 66.687, ±.0015. 



Hence Mo = 96.088. 



This mean may be combined with former determinations thus : 



Dumas 66.649, ± .0300 



Debray 66.556, ± .0200 



Rammelsberg 66.708, ± .0680 



Seubert and Pollard 66.668, ± .0022 



Vandenberghe 66.687, ± .0015 



General mean 66.681, it .0012 



Neglecting all determinations made before 1859, there are now throe 

 ratios from which to compute the atomic weight of molybdenum, as 

 follows : 



(1). MoO., : Mo :: 100: 66.681, ± .00i2 



(2). 2AgCl:Mo03: : 100: 50.202, ± .0018 



(3). Na,MoO,:2NaCl: : 100: 56.745, ± .0017 



Reducing these ratios with Ag = 107.880, ±.00029, CI = 35.4584, ± 

 .0002, and Na = 23.0108, ±.00024, we have— 



From ratio 2 Mo = 95.917, ± .0052 



" 3 96.055, ± .0036 



" 1 96.062, ± .0039 



General mean, Mo = 96.029, ± .0024 



In this combination the actual uncertainty is greater than the deci- 

 mals. For practical purposes the round number 96 can be used. 



^ Acad. Roy. Beige, Mf^ni. Couronngs, T. 56. 



