vii THE BURNING OF INFLAMMABLE AIR 135 



oxide to oxidise the hydrogen and measuring the weight of 

 water produced and the loss in weight of the copper oxide 



They found the ratio 



Oxygen : hydrogen = W\ : 1. 



This method was used on a large scale by Dumas in 1842. He 



purified the hydrogen 



from sulphuretted hydrogen by means of lead nitrate solution ; 



from arseniuretted hydrogen by means of silver sulphate solution ; 



from acid vapours by means of potash ; 



from water-vapour by means of oil of vitriol cooled in ice, or 



by means of phosphoric oxide ; 



these purifying agents were contained in seven U-tubes, each 

 i metre in height. The copper oxide and copper were 

 weighed in a large vacuous bulb provided with a beak one 

 metre in length ; during the reduction the bulb was heated by 

 a large spirit lamp. In 19 experiments Dumas prepared one 

 kilogram of water and found the ratio 



Oxygen : hydrogen = 7 '98 : 1. 



Scott, in 1893, reverted to the method used by Monge. He 

 exploded pure hydrogen and oxygen and found the combining 

 volumes to be in the ratio 2*00245 : 1. When combined with 

 densities measured by Rayleigh, this gave the composition 



Oxygen : hydrogen = 7 '931 : 1. 



Morley, in 1895 (i), by weighing the gas in large globes 

 containing 22 litres found the density of oxygen to be 



1*42900 grams per litre at o C. and 760 mm. pressure. 



(2) By measuring the pressure produced in three globes of 

 43 litres capacity when a known weight of hydrogen was 

 expelled from palladium, he found the density of hydrogen to be 



0*089873 gram per litre at o C. and 760 mm. pressure. 



(3) By exploding a mixture of hydrogen and oxygen he found 

 the combining volumes to be in the ratio 2*00269 : 1 at o C. 

 Whence the composition by weight is found to be 



Oxygen : hydrogen = 1'^^ : 1. 



(4) By burning together in a special combustion - chamber 

 known weights of hydrogen and oxygen (weighed as in the 



