by the presence of mercury vapour. In the final series of 

 experiments, therefore, the gas was weighed in a tube filled 

 with metallic palladium (Fig. 30) ; l on heating the tube the 

 gas was expelled into three large globes immersed in ice ; the 

 pressure produced in these globes by a known weight of gas 

 was measured. In a typical experiment the data were : 



Volume of three globes... ... ... ... 43*2574 litres. 



,, ,, air space in manometer ... ... 0-0536 ,, 



,, ,, leads 0*0365 ,, 



Temperature, o C. Total volume ...-43-3475 ,, 



Pressure (corr.), 725-30 mm. Weight = 3 7 158 grams. 

 Density of hydrogen 0-089864 gram per litre. 



Twenty-five experiments made in this way gave an average 

 value 



0-089873 0-0000027. 



In order to find the weights of the gases which combined 

 together to form water, it was necessary next to determine 



FIG. 30 MORLEY'S PALLADIUM-TUBE FOR WEIGHING HYDROGEN. 



a Is a bulb containing 600 grams of palladium ; b contains phosphoric 

 anhydride to dry the gas ; c is a seal of fusible metal. 



the ratio of their combining volumes. For this purpose 

 Morley prepared a mixture of the two gases by passing an 

 electric current through dilute potash cooled in ice. The 

 apparatus was provided with drying tubes and a tap, and 

 was arranged so that it could be weighed 'before and after 



1 Morley used 600 grams of palladium ; he found that this quantity 

 absorbed 3*8 grams of hydrogen and liberated 37 grams, occupying 

 over 40 litres. This method of purifying and weighing hydrogen was 

 introduced by Chirikoff in 1882 ; it forms one of the most important 

 of the advances that have been made in the methods of determining 

 the composition of water since the work of Dumas. 



