﻿318 Mr. Baly and Dr. Ramsay on the Relations of Pressure, 

 Table {continued). 



No. of 

 Stroke. 



Vacuum. 



Ratio of 



Grauge 



Readings 



E 



F' 



Factor of 



ICxhaustion 



from gauge 



E. 



Factor of 



Exhaustion 



from gauge 



F. 



Theory. 

 V. 



V + V. 



6th Series. 



Preliminary. 



•004 

 •0024 



10549 

 10741 

 1-091 

 1101 



•5639 

 •5681 

 •6530 



•5486 

 •5630 

 •6494 



•548 



ir 



in 





7th Series. 



I 



Very high 

 vacuum. 





•5875 

 •7362 

 •5857 

 •5631 

 •6510 



•5583 

 •7670 

 •5912 

 •6012 

 •5735 



•590 

 »» 

 >> 



II 



in 



IV 



v 









The last series vary a great deal owing to difficulties of 

 reading, and also to the fact of the extremely high vacuum, 

 pumping is performed by diffusion. The presence of mercury- 

 vapour makes no difference in these experiments at all. When 

 the mercury is raised in the gauges and the pressure on the gas 

 rises, the mercury-vapour becomes condensed, and readings 

 are only made of the hydrogen in the apparatus. When the 

 mercury is lowered again, mercury-vapour doubtless mixes 

 with the hydrogen till a state of equilibrium is reached, the 

 percentage of mercury- vapour depending on the pressure. 

 In working the pump also the presence of mercury-vapour 

 has no effect, for the pump-chamber when the mercury falls 

 is empty of hydrogen, and if there is any hydrogen in the 

 apparatus it will diffuse in through the mercury-vapour. 

 This explains how it is possible to exhaust an apparatus rilled 

 with hydrogen so far that the pressure of the gas left is con- 

 siderably below the pressure of mercury-vapour, though of 

 course the actual pressure in the apparatus is not below that 

 of mercury- vapour, for as fast as the hydrogen diffuses out of 

 the apparatus into the pump, its place is taken by more 

 mercury-vapour. Apparently, however, there is a limit to 

 this, for we were not able to take out any more hydrogen 

 than is represented by the last reading of the table above. 

 The pressure of hydrogen in the apparatus was about '000076 

 millim., while the vapour-pressure of mercury is about 

 •0002 millim. 



