142 THE ATOMIC WEIGHTS. 



For the pentachloride the following quantities balance 

 100 of AgCl : 



MoCl^. MoS^. 



38.168 22.428 



3S.057 22.289 



Mean, 38.112, ± .038 Mean, 22.3585, ± .040 



Hence MoCl^ = 272.587, ± .271, and MoS, = 159.914, 



± .287. 



We have now the molecular weight of each chloride, and 

 three values for that of the disulphide. Combining the lat- 

 ter we get a general mean, as follows : 



From MoCU series MoS.^ = 159.652, dz .268 



•' MoCl^ " •' = 159-964, =t -627 



" MoCI- " •' = 159.914, dz .287 



General mean " ^= 159.790, dr .187 



With these data, in addition to those given by Dumas 

 and by Debray, we get live estimates of the atomic weight 

 of molybdenum : 



Dumas and Debray's data Mo =; 95.429, ifc .057 



From molecular weight of M0CI2 "' "= 96.262, dz .190 



MoCl^ ■' =95.434,^.363 



MoCl^ ■• ^95.737,^.280 



MoS.^ " = 95.816, zb .1S8 



General mean " =95.527,^.051 



Or, if O = 10, Mo = 95.747. 



It will at once be seen that the most reliable results arc 

 those obtained by the reduction of molybdenum trioxide. 

 Traces of oxychlorides may possibly have contaminated the 

 chlorides and augmented their atomic weight. Our final 

 figure, therefore, may be a trifle too high, but the early 

 value, 92, is unquestionabl}' very far too low. 



Since the foregoing discussion was written a single exj^eri- 

 ment by Rammelsberg * has been brought to my notice. 



* Berlin Monatsbericht, 1877, 574. 



