Mr. T. Graham on the Molecular Mobility of Gases. 431 



The increase of oxygen is 3*5 per cent. ; that is, an increase of 

 16*7 upon 100 oxygen originally present in the air. 



With the single pipe-stalk, 24 inches long, first described, the 

 oxygen of atmospheric air was concentrated about 2 per cent, 

 when one litre was transmitted in one hour. Of 450 cub. centims. 

 of air collected in that time, the composition proved to be 



Oxygen .... 23*12 

 Nitrogen .... 76-88 



10000 



About 9 litres were drawn into the vacuum at the same time. 



The separation of the gases of atmospheric air is a severe trial 

 of the powers of the atmolyser, owing to the small difference in 

 the specific gravities of these gases. But where a great disparity 

 in density exists, the extent of the separation may become very 

 considerable. 



Several experiments were made upon a mixture of equal 

 volumes of oxygen and hydrogen carried through the single tube 

 atmolyser, 24 inches in length. 



1. Of the mixture described, 7*5 litres entered the tube and 

 0*45 litre was collected in one experiment. The mixture was 

 composed as follows : — 



Oxygen. Hydrogen. 



Before traversing the atmolyser .50 +50 



After traversing the atmolyser . . 92*78 + 7*22 



2. In another similar experiment, 14 litres of the mixed gas 

 entered the tube and 0*45 litre was delivered in a period of 

 two hours. The result was — 



Oxygen. 



Hydrogen. 



50 



+ 50 



95 



+ 5 



Before traversing the atmolyser 

 After traversing the atmolyser 



Here the proportion of hydrogen is reduced from 50 to 5 per 



cent. 



3. Of the explosive mixture, consisting of 1 volume oxygen 



and 2 volumes hydrogen, 9 litres were transmitted and 0*45 litre 



collected in one hour. The change effected was found to be as 



follows : — 



Oxygen. Hydrogen. 



Before traversing the atmolyser . 33*33 -f 66*66 

 After traversing the atmolyser . . 90*7 + 9*3 



The result in such experiments is striking, as the gas ceases to 

 be explosive after traversing the porous tube, and a lighted taper 



