MOLYBDENUM. 137 



For copper we have- 



From composition of CuO Cu ^ 63.181, ±: .036 



" CuSOj, (Hampe) " = 63.171, ± .012 



General mean " = 63.173, ± .011 



If = 16, then Cu becomes = 63.318. 



The close agreement between the two independent values 

 for Cu is certainly very striking. It will be seen that 

 Hampe's two estimates upon the sulphate carry (perhaps 

 accidentally) much greater weight than all the experiments 

 upon the oxide. This might seem like giving them undue 

 credit, were it not for the fact of the remarkable concordance 

 of the results above referred to. Either estimate for Cu 

 would be valid without the other. 



MOLYBDENUM. 



If we leave out of account the inaccurate determination 

 made by Berzelius,* we shall find that the data for the 

 atomic weight of molybdenum lead to two independent esti- 

 mates of its value ; one near 92, the other near 96. The 

 earlier results found by Berlin and by Svanberg and Struve 

 lead to the lower number ; the more recent work of Debray, 

 Dumas, and Lothar Meyer sustains the higher. The latter 

 value is the more probable, although both may be vitiated 

 by constant errors in opposite directions. 



The earliest investigation which we need especially to 

 consider is that of Svanberg and Struve.f These chemists 

 tried a variety of different methods, but finally based their 

 conclusions upon the two following: first, molybdenum 

 trioxide was fused with potassium carbonate, and the car- 

 bon dioxide which was expelled was estimated ; secondly, 

 molybdenum disulphide was converted into the trioxide by 



* Poggend. Annal., 8, I. 1826. 



f Journ. fiir Prakt. Chem., 44, 301. 1848. 



