Knowledge. 



With which is incorporated Hardwicke's Science Gossip, and the Ilhistratcd Scientific News. 



A Monthly Record of Science. 



Conducted by Wilfred Mark \\\h!). F.L.S., and E. S. Grew, M.A. 



M.w, lyii. 



AN LM14{0\ED TOEPLER PUMP. 



Hy H. J. GR.\Y. 



\Vhi:n working with a Toepler pump in the produc- 

 tion of high vacuua, the necessity to refill the mercury 

 reservoir from time to time is a source of incon- 

 venience. To remedy 

 this defect the writer 

 has successfully adopted 

 the device described 

 in the following para- 

 graphs. 



The principle will be 

 esident from Figure 183, 

 which represents the 

 essential features of 

 a typical form of Toepler 

 pump. Instead of a 

 single reservoir, two 

 equal mercury-contain- 

 ers are used. These, 

 it will be seen, are 

 connected to the 

 branches of a Y tube 

 fixed in an inverted 

 position. Each branch 

 should bi' tapped or, 

 as a substitute, strong 

 but easilv operated 

 spring clips might be 

 used on the india-rubber 

 connecting tubes. A 

 screw clip would be too 

 troublesome. 



The receptacle, C, 

 containing the end of 

 the eject tube, has a 

 tubulure at the side, 



Figure 1S3. .-^n Improved Toepler I'nnip. 

 into which is fixed a perforated rubber cork, having provided w ith a mercury trap if considered advisable 



one end of a bent glass tube passed through it. 

 To the lower end of this is fixed a short rubber tube 

 and glass jet. Let the reservoir, .\, be filled with 

 mercury, raised and supported in an appro- 

 priate manner. The tai). D, being open, 

 the mercury passes through the pump in 

 the ordinarv manner and ultimately reaches 

 the vessel. C. Overfiowiiig through the 

 bent glass tube it falls into the second 

 reservoir, B. which is supported imme- 

 diately beneath, the tap, E, being kept 

 closed. Thus one reservoir is always 

 filling automatically, while the other is 

 discharging. When A has become empty 

 it is the work of a moment to raise the 

 mercury for another fall. Simply reverse 

 the position of the reservoirs, always 

 opening the tap communicating with the 

 nil one and closing the other. It is 

 lilt necessary to fit a tap to the vessel C, 

 since the mercury is always 

 flowing through the bent tube 

 except for the moment while 

 the reservoirs are being changed, 

 when the short rubber tube 

 may be closed by 

 pressure between the 

 fingers. 



.\ three-wa\' tap ma\' 

 be substituted for the 

 tapped Y-piece with 

 equally good results. 

 It should have a bore 

 of about two milli- 

 metres, and may be 



