140 THE ATOMIC WEIGHTS. 



was raised sufficiently to insure a complete reduction. From 

 the weighings I calculate the percentages of metal in M0O3 : 



In 1868 the same method was employed by Debray.* His 

 trioxide was purified by sublimation in a platinum tube. 

 His percentages are as follows : 



5.514 grm. M0O3 gave 3.667 grm. Mo. 66.503 percent. 



7.910 " 5.265 " 66.561 



9.031 " 6.015 " 66.604 " 



Mean, 66.556, db .020 



This mean, combined with that of Dumas', gives a gen- 

 eral mean of 66.585, ±: .017. 

 Hence Mo = 95.429, ± .057. 



Debray also made two experiments upon the precipitation 

 of molybdenum trioxide in ammoniacal solution by nitrate 

 of silver. In his results, as published, there is curious dis- 

 crepanc}', which, I have no doubt, is due to typographical 

 error. These results I am, therefore, compelled to leave out 

 of consideration. They could not, however, exert a very 

 profound influence upon the final discussion. 



The most recent investigation upon the atomic weight of 

 molybdenum is the discussion by Lothar Meyer f of the 

 experimental results obtained by Liechti and Kempt in 

 their analyses of the chlorides. Of these compounds there 

 are four : MoCl , , MoCl 3 , MoCl ^ , and MoCl 5 . The chlorine in 

 each was estimated as silver chloride, and the molybdenum 

 as disulphide. From these analyses Meyer deduces three 



* Compt. Rend., 66, 734. 

 f Ann. Chem. Pharm., 169, 365. 1873. 

 • + .\nn. Chem. Pharm., 169, 344. 



