Sparking -Potentials  in  Carbon  dioxide  and  Nitrogen. 
545 
few  seconds,  and  in  no  case  was  sparking  allowed  to  be  more 
than  momentary.  It  was  found  that  unless  these  conditions 
were  complied  with,  other  phenomena  occurred  which  made 
the  determination  of  the  sparking-potential  uncertain.  These 
phenomena  were  especially  noticeable  in  the  neighbourhood 
of  the  minimum  sparking-potential,  and  at  values  of  pd  less 
than  the  critical  value,  p  being  the  pressure  and  d  the  distance 
between  the  plates. 
The  results  of  all  the  experiments  are  collected  in  the 
following  tables,  in  which  are  given  the  potentials  required 
to  produce  sparks  with  ultra-violet  light  acting,  the  potentials 
required  without  light,  and  in  some  cases  the  potentials 
calculated  for  the  distance 
logs- log  ff 
Carbon  dioxide. 
Pressure. 
P 
Distance 
between 
plates  d. 
cm. 
pd. 
Calculated 
potential. 
Xd. 
Spark  potential 
with  light. 
Spark  potential 
without  light. 
mm. 
Tolts. 
volts. 
volts. 
2 
•369 
•738 
516 
517 
1 
•736 
•736 
516 
509 
525 
1 
•571 
•571 
500 
495 
509 
1 
•465 
•465 
488 
491 
•5 
•929 
•464 
488 
485 
■5 
•706 
•353 
494 
497 
•5 
•613 
•306 
537 
530 
542 
•25 
1-062 
•265 
558 
564 
Nitrog< 
m  prepared  by  first  method. 
V 
(with  light). 
Spark 
p. 
d. 
pd. 
Xd. 
potential 
without  light. 
mm. 
cm. 
volts. 
volts. 
volts. 
4 
•708 
2-832 
496 
494 
4 
1-236 
4944 
649 
2 
1-41 
2-82 
493 
2 
•67 
134 
352 
349 
1 
•88 
•88 
308 
303 
305 
1 
•601 
•601 
316 
311 
311 
•5 
1-195 
•597 
314 
