678 



Lord Rayleigh on the Proportion of 



proportion of oxygen being maintained suitably by additions 

 of oxygen or hydrogen as might be required. In the latter 

 case the feed should be very slow, and the electric discharge 

 should be near the top of the test-tube. Great care is 

 required to prevent the hydrogen getting into excess ; for if 

 this should occur, the recovery of the normal condition by 

 addition of oxygen is a very risky process. After sufficient 

 gas from the holder, usually about 2 litres, had been 

 introduced, the discharge was continued until no more 

 nitrogen remained, as was evidenced by the cessation of 

 contraction and by the disappearance of the nitrogen line 

 from the spectrum of the discharge when the terminals were 

 connected with a leyden-jar. When it was certain that all 

 nitrogen had been removed, the residual oxygen was taken 

 up by ignition of a piece of phosphorus. On cooling, the 

 residue of argon was measured, and its amount expressed as 

 a percentage of the total gas taken from the holder. 



The results are shown in the following table. The oxygen, 

 expressed as a percentage of the whole, varied from 30 to 

 about 98. From 43 to 90 per cent, of oxygen, the argon, 

 as a percentage of the whole, scarcely varied from 2*0. 



1 

 Percentage of Percentage of Argon as a percentage of 

 Oxygen. Argon. j the Nitrogen and Argon. 



30 

 43 

 64 



75 

 90 



1-3 



2-0 

 2-0 

 2-1 

 2-0 



1-9 

 3-5 



5-6 



8-4 



20-0 



98 -76 

 100 o-o 



1 



33-0 

 100-0 



The experiment entered under the head of 98 per cent, 

 oxygen is not comparable with the others. In this case 

 5 J litres of gas were collected as the last portion coining 

 away from a stock of liquid as it dried up. Nor w^as the 

 subsequent treatment quite parallel, for the whole of the 

 oxygen was first removed with copper and ammonia leaving 

 125 c. c. of mixed nitrogen and argon, of which again by 

 subsequent analysis 42 c. c. was found to be argon. The last 

 entry corresponding to 100 per cent, of oxygen is theoretical 

 and does not represent any actual experiment. 



It must be clearly understood that these results relate to 

 the vapour rising from the liquid, and not to the composition 

 of the liquid itself. So far as the oxygen content is concerned, 



