Sparking -Potentials  in  Carbon  dioxide  and  Nitrogen.      549 
Fig.  3  shows  the  curves  obtained  with  the  different 
samples  of  nitrogen  and  also  the  effect  of  small  quantities  of 
oxygen. 
Fig.  3. 
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d  measured  in,  cms. 
The  theoretical  investigations  are  intended  to  apply  to  cases 
where  the  pressure  is  not  less  than  the  critical  pressure,  and  ir 
will  be  noticed  that  the  effect  o£  small  impurities  is  negligible 
at  the  higher  pressures. 
The  minimum  spark-potential  for  the  first  nitrogen  is  about 
302  volts,  for  the  second  about  295  volts.    The  gas  containing 
