828 



By the aid of this arrangement it is now possible to fill the 

 measuring tube, which is fastened at JV on the piece M with the 

 gas that is to be measui-ed, this glass tube being always subjected 

 to the same pressure on tlie inside and on the outside. 



After the whole system of tubes and all the cocks etc. have been 

 cleaned, the mercury vessel R is filled entirel}^ and the vessel D 

 half with mercury. By the application of a slight pressure the 

 mercury in Q rises, and tills the whole tube Q up to the cock H. 

 Then the cock T is closed, so that the mercury in Q cannot move 

 up and down any longer. Wiien this |)ressure is applied, the vessel 

 L outside the glass tube has tilled with the oil, which is used as 

 pressure transmission liquid. Now all the cocks except T'are opened, 

 and the whole system A abc F'FON is exhausted by means of the 

 GAEDE-pump. Then the mercury from D rises in the jar (r and 

 reaches barometric height between F and F' . Now the apparatus 

 may be rinsed once or twice with gas by admitting gas at B by 

 means of the mercury reservoir, and then making a vacuum with 

 the GAEDK-pump. If we now want to bring a definite measured 

 quantity of gas into the measuring tube, we close a, and admit a 

 quantity of gas into A. When the mercury reservoir is then raised, 

 a quantity of gas is isolated in A, the pressure, the volume, and the 

 temperature of which can be determined. If now the glass cock a 

 is opened, the gas flows into the exhausted space cF'. Now the 

 mercury in F falls, and by raising the mercury reservoir which is 

 in communication with B, we can now expel the gas from A to 

 D. If we want to do this quantitatively, we must raise the mercury 

 reservoir so much that the mercury overflows at b, and fills the 

 whole tube, be, and that at last it becomes visible at the upper end 

 of F. C is then closed. The gas is then under a pressure of about 

 one atmosphere in the jar D, and further in FON and in the 

 measuring tube. 



By the hydrostatic pr^ss, resp. through the way S, US^ P/e we 

 now increase the pressure. The mercury in D then descends outside 

 the jar G and rises inside it, and expels the gas more and more 

 from the jar towards F. The pressure in the measuring tube then 

 rises, of course. But U being in communication with L through S^, 

 the pressure inside and outside the measuring tube is always the 

 same. If we want to convey quantitatively, the pressure must be 

 raised so high that the gas has been entirely expelled by mercury 

 from G and F, and the mercury has reached the steel capillary 

 above F and finally H. Then H is closed. Now the communication 

 between the inside and the outside of the measuring tube is broken. 



