XVI. STABLE ISOTOPES AS TRACERS 



575 



the barometric level. The evacuated storaj^e flask W has a volume of 10 to 

 12 liters and is convenient for lowering the mercury level in }'. The gas 



Fig. 2. Schematic diagram of a Xier type mass spectrometer, including electrical 



circuits and auxiliary equipment. 



from Y is admitted slowly and continuously into the mass spectrometer 

 ionization box, A", through the very fine leak, L {13). 



Current to filament F is supplied by storage battery Bz and indicated by 



