16 



THE ATOMIC WEIGHTS. 



A second phosphorus pentoxide tube served to prevent the sucking back 

 of moisture from the external air. The loss in weight of the palladium 

 tube, corrected by the gain in weight of the first phosphorus pentoxide, 

 gave the weight of hydrogen taken. The gain in weight of the two col- 

 lecting tubes gave the weight of water formed. All weights in the follow- 

 ino; table of results are reduced to a vacuum : 



In sum, 6.55880 grammes of hydrogen gave 52.30383 of water, whence 

 O = 15.9492. 



In March, 1889, Lord Rayleigh * published a few determinations of the 

 atomic weight of oxygen obtained by still a new method. Pure hydrogen 

 and pure oxygen were both weighed in glass globes. From these they 

 passed into a mixing chamber, and thence into a eudiometer, where they 

 were graduall}^ exploded by a series of electric sparks. After explosion 

 the residual gas remaining in the eudiometer was determined and meas- 

 ured. The results, given without weighings or explicit details, are as 

 follows : 



15-93 

 15-98 

 15-98 

 15-93 

 15.92 



Mean, 15. c 



=b .009 



Correcting this result for shrinkage of the globes and consequent change 

 of tare, it becomes = 15.89, ± .009. 



• In the same month that Lord Rayleigh 's paper appeared, Noyes f pub- 

 lished his first series of determinations. His plan was to pass hydrogen 

 into an apparatus containing hot copper oxide, condensing the water 

 formed in the same apparatus, and from the gain in weight of the latter 

 getting the weight of the hydrogen absorbed. The apparatus devised for 



*Proc. Roy. Soc, 45, 425. 



t Amer. Chem. Joiirii., 11, 155. 



