LECTURES. 43 



obeyed the various tests for Nitrogen must obviously be a different 

 substance, as no amount of coaxing would induce it to combine 

 with Oxygen. 



The method employed was to pass a stream of electric sparks 

 through a mixture of O.vygen and Atmospheric Nitrogen contained 

 in a flask inverted over a weak Solution of Caustic Soda, which 

 absorbed the oxide as soon as it was formed. Although the 

 modern apparatus worked 3,000 times faster than Cavendish's 

 original one, it took nine days to obtain four cubic inches of the 

 inert residue. 



Another method of separating this new body was devised by 

 Professor Ramsay, who now joined in the research. 



Nitrogen from the air was first passed over red hot Copper to 

 remove the last traces of oxygen and then through tubes containing 

 red hot Magnesium, which combines with true Nitrogen. It was 

 found difficult to get rid of the last traces of this gas by this 

 method, so that the process concluded with passing electric sparks 

 through it in presence of Oxygen. The yield in this case was 

 greater than before, some thirty cubic inches being obtained in a 

 week. 



A third method consists in passing " atmospheric nitrogen " 

 through a dozen long clay pipes connected in series and surrounded 

 by a glass cylinder partially exhausted. In this way the lighter of 

 the gases (true Nitrogen) diifuses through the porous clay into the 

 cylinder, leaving the heavier gas mixed with less true Nitrogen than 

 before in the pipes' stems. 



This does not effect a complete separation, but as before the 

 product has to be mixed with oxygen and sparked through. 



Having by one or other of these laborious methods got rid of 

 the true Nitrogen, the first experiment with the residual gas was the 

 finding of its Vapour Density. 



It was found to be 20 ; that of pure Nitrogen being 14, and of 

 Hydrogen i. The amount of the gas present in the air was about 

 I per cent, by volume and this exactly accounted for the discre- 

 pancy between the densities of " atmospheric " and " chemical " 

 Nitrogen from the observation of which the discovery originated. 



Experiments on the gas were then performed to discover its 

 properties. These brought out the remarkable result that (up to 

 the present) under no condition and with no element, compound 

 or mixture, will it enter into chemical combination. Hundreds of 

 substances have been tried including the most energetic but in 



