426 Lord Rayleigh. [Mar. 7, 



Mr. Keiser describes experiments from which it appears that palladium 

 will not occlude nitrogen a very probable impurity in even the most 

 carefully prepared gas. My palladium was placed in a tube sealed, as 

 a lateral attachment, to the middle of that containing the phosphoric 

 anhydride ; so that the hydrogen was submitted in a thorough manner 

 to this reagent both before and after absorption by the palladium. Any 

 impurity that might be rejected by the palladium was washed out 

 of the tube by a current of hydrogen before the. gas was collected for 

 weighing. But as the result of even this treatment I have no improve- 

 ment to report, the density of the gas being almost exactly as before. 

 Hitherto the observations have related merely to the densities of 

 hydrogen and oxygen, giving the ratio 15*884, as formerly explained. 

 To infer the composition of water by weight, this number had to 

 be combined with that found by Mr. Scott as representing the ratio 

 of volumes. The result was 



The experiments now to be described are an attempt at an entirely 

 independent determination of the relative weights by actual combus- 

 tion of weighed quantities of the two gases. It will be remembered 

 that in Dumas's investigation the composition of water is inferred 

 from the weights of the oxygen and of the water, the hydrogen being 

 unweighed. In order to avoid the very unfavourable conditions of 

 this method, recent workers have made it a point to weigh the 

 hydrogen, whether in the gaseous state as in the experiments of 

 Professor Cooke and my own, or occluded in palladium as in Mr. 

 Keiser's practice. So long as the hydrogen is weighed, it is not very 

 material whether the second weighing relate to the water or to the 

 oxygen. The former is the case in the work of Cooke and Keiser, the 

 latter in the preliminary experiments now to be reported. 



Nothing could be simpler in principle than the method adopted. 

 Globes of the same size as those employed for the density determina- 

 tions are filled to atmospheric pressure with the two gases, and are 

 then carefully weighed. By means of Sprengel pumps the gases are 

 exhausted into a mixing chamber, sealed below with mercury, and 

 thence by means of a third Sprengel are conducted into a eudio- 

 meter, also sealed below with mercury, where they are fired by 

 electric sparks in the usual way. After sufficient quantities of the 

 gases have been withdrawn, the taps of the globes are turned, the 

 leading tubes and mixing chamber are cleared of all remaining gas, 

 and, after a final explosion in the eudiometer, the nature and amount 

 of the residual gas are determined. The quantities taken from the 

 globes can be found from the weights before and after operations. 



