XVI. 



STABLE ISOTOPES AS TRACERS 



579 



deuterium, the hydrogen molecule itself has been found most con- 

 venient, even though the analyses are rather complicated (5, p. 99). 



TABLE II 

 Mass Spectra of Some Ions" Usually Observable in Common Test Gases 



"All ions carry a single positive charge unless indicated otherwise. 



In very dilute samples of deuterium, the ions that occur in readily 

 measurable concentrations are listed in the second column of Table 

 II ; in the very concentrated deuterium samples, in the third column. 



