TUNGSTEN. 259 



Reduction Series. 



2.0738 grm. WO3 gave 1.6450 W. 79-323 per cent. 



4.0853 " 3-2400 " 79-309 



6.1547 " 4.88U " 79.307 " 



Oxidation Series. 



1.5253 grm. W gave 1.9232 WO.^. 79-3" per cent. 



3.1938 " 4-0273 " 79-304 " 



4.7468 " 5-9M " 79-314 " 



Mean of all, 79.311, zh .0018 



Hence with = 16, W = 184.007. 



In order to account for the difference between this result and that of 

 Pennington and Smith, an impurity of molybdenum trioxide amounting 

 to about one per cent, would be necessary. Schneider suggests that the 

 quantities of material used by Pennington and Smith were too small, and 

 that there may have been mechanical loss of small particles during the 

 long heatings. Such losses would tend to raise the atomic weight com- 

 puted from the experiments. On the other hand, the losses could hardly 

 have been uniform in extent, and the extremely low probable error of 

 Pennington and Smith's series renders Schneider's supposition improb- 

 able. The error, if error exists, must be accounted for otherwise. 



Since Schneider's paper appeared, another set of determinations by 

 Shinn * has been published from Smith's laboratory. Attempts to verify 

 the results obtained by Smith and Desi having proved abortive, and other 

 experiments having failed, Shinn resorted to the oxidation method and 

 gives the subjoined data. The percentage column is added by myself: 



.22297 grm. W gave .28090 WO,. 79-377 



.17200 " .21664 " 79-394 



.10989 " .13844 " 79.377 



.10005 " -I2598 " 79.417 



Mean, 79.391, ± .0066 



This figure is very close to that found in Pennington and Smith's series, 

 and therefore serves as a confirmation. The discordance between these 

 results and Schneider's is still to be explained. 



There are still other experiments by Riche,t which I have not been 

 able to get in detail. They cannot be of any value, however, for they 

 give to tungsten an atomic weight of about ten units too low. We may 

 therefore neglect this series, and go on to combine the others : 



Berzelius 79-7745, =!= -0880 



Schneider, 1850 79-320, d= .0068 



Marchand 79.3205, H= .0073 



V. Borch 79-293, ± .0108 



Dumas 79-3 ' 2, i .0090 



* Doctoral thesis., University of Pennsj'lvania, 1896. " The atomic mass of tungsten." 

 t Journ. fiir Prakt. Cheui., 69, 10. 1857. 



