ATOMIC WEIGHTS 19 



were both weighed in glass globes. From these they passed into a mixing 

 chamber, and thence into a eudiometer, where they were gradually ex- 

 ploded by a series of electric sparks. After explosion the residual gas 

 remaining in the eudiometer was determined and measured. The results, 

 given without weighings or explicit details, are as follows : 



15.93 

 15.98 

 15.98 

 15.93 

 15.92 



Mean, 15.948, ± .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 Eayleigh's paper appeared, W. A. ISToyes ' 

 published his first series of determinations. His plan was to pass hydro- 

 gen 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 

 this purpose consisted essentially of a glass bulb of 30 to 50 ec. capacity, 

 with a stopcock tube on one side and a sealed condensing tube on the 

 other. In weighing, it was counterpoised by another apparatus of nearly 

 the same volume but somewhat less weight, in order to obviate reduc- 

 tions to a vacuum. After filling the bulb with commercial copper oxide 

 (90 to 150 grammes), the apparatus was heated in an airbath, exhausted 

 by means of a Sprengel pump, cooled, and weighed. It was next re- 

 placed in the airbath, again heated, and connected with an apparatus 

 delivering purified hydrogen. When a suitable amount of the latter had 

 been admitted, the stopcock was closed, and the heating continued long 

 enough to convert all gaseous hydrogen within it into water. The appa- 

 ratus was then cooled and weighed, after which it was connected with a 

 Sprengel pump, in order to extract the small quantity of nitrogen which 

 was alwaj's present. The latter was pumped out into a eudiom.eter, 

 where it was measured and examined. The gain in weight of the appa- 

 ratus, less the weight of this very slight impurity, gave the weight of 

 hydrogen oxidized. 



The next step in the process consisted in heating the apparatus to expel 

 water, and weighing again. After this, pure oxygen was admitted and 

 the heating was resumed, so as to oxidize the traces of hydrogen which 

 had been retained by the copper. Again the apparatus was cooled and 

 weighed, and then reheated, when the water formed was received in a 



1 Amer. Chem. Journ., H, 155. 1889. 



