XVI. STABLE ISOTOPES AS TRACERS 



577 



either 60, 90, or 180°. An instrument of the 90° type, but other- 

 wise closely similar to the 60° design of Figure 2, was once built com- 

 mercially and has been described by Hippie (^, p. 551). The popular 

 180° design originated by Dempster has been adopted for the auto- 

 matically recording commercial mass spectrometer (7,34) dia- 



Liquid 



Samples To Pump 



llfl 



Break- 

 off 



Metering 



Volume In' 

 Gas Samples! 



Recording Oscillograph 



P 



u iUU 



.*- Record 

 Galvan. 



-^^^ 



;^ 



Lamp 



Inlet 



Sample 



Bottle 



J 



500 to 

 3000 

 Volts 



Variable 



Amplifier _ 



Analyzer Tube 



Fig. 3. Schematic diagrtini of llie 180° Consolidated i^ugineering Company 



mass spectrometer (7). 



grannned in l^'igure 3 and fui- others {5,12). 1^'igure 3 is probably 

 self explanatory but it appears deceptively simple since the numerous 

 and complex electronic circuits are not included. Neither is the 

 magnet, which must produce a uniform magnetic- field sufficiently 

 large to cover the entire region occupied by the tuV)e and not merely a 

 small central sector, 



