DHNSITIES OK OXYCJEN AND II YDKCKiKN. 0( 



2. DETERMINATION OK DKNSITY J!Y KIKST MI'VIIKH). 



In the first series of determinations of the density of hydrogen, nearly all the 

 manipulation was almost precisely the same as that used in the fii'st series of deter- 

 minations of the density of oxygen. The two were carried on al. the same time, 

 with the same apparatus in the same condition ; it was ho|)ed that in this manner 

 of working the ratio of the two densities might be subject to fewer systematic 

 errors. OuIy a brief account is therefore requiretl. 



8. KlUST JIETIIOD. J'llEl'AKATION OK ilYUKOGEN. 



In all the experiments of this series, hydrogen was pi-epared by the electrolysis 

 of pure dilute sulphuric acid. The gas was passed thi-ough a strong solution of 

 potassium hydroxide, over incandescent copper, and through three drying tubes 

 one metre loner and two and a half centimetres in diameter, the last filled with 

 phosphorus pentoxide and the preceding one with powdered potassium hydroxide. 

 In the appaiatus up to this point, the pressure was always kept equal to that of 

 the atmosphere by a stopcock and a manometer. 



In some experiments of this series the gas was admitted at once to the globe 

 as it issued from the regulating stopcock. In the remaining experiments, the gas 

 was first absorbed in metallic palladium. When this was to be filled with hydrogen, 

 it was fiist heated in a vacuiun. Then hydrogen was passed through it while it 

 was still too hot to absorb the gas, and the current was continued for some time, 

 after which the source of heat was removed. After the absorption was complete, 

 a current of gas was passed for a long time to expel any gas other than hydrogen 

 which might have accompanied the latter. When this end was thought to have 

 been attained, the eonuectiou between the palladium and the voltameter was cut 

 off, and the connection opened to deliver the hydrogen into the globe. Heat being 

 applied to the palladium, the globe was filled. 



In all the experiments in which palladium was used, the tubes for conducting 

 the gas were closed, either by fusion or by fusible metal plugs, so that leakage from 

 the atmosphere into the apparatus was absolutely excluded. 



4. KIKST iMETUOD. I'ROOK OK THE PURITY OF THE HYDROGEN. 



The voltameter in which hydrogen was produced contained about five litres 

 of dilute sulphuric acid, and the drying tubes and other parts of the apparatus 

 had a capacity of one or two litres more. To remove the air from this apparatus 

 took of course a considerable time. It was thought jiroper to meet any objections 



