Conductivity  of  Metallic  Oxides. 
523 
impossible  to  test  for  a  polarization  current  because  of  a 
thermoelectric  effect  due  to  one  face  of  the  oxide  being 
slightly  warmer  than  the  other.  A  current  of  about  *25 
ampere  was  sent  through  the  oxide  at  700°  C.  The  galvano- 
meter deflexion  remained  steady  except  on  one  occasion  when 
it  decreased  slightly.  In  no  case  did  the  current  fall  off  as  it 
had  done  in  the  experiments  with  lime,  so  that  we  may  con- 
clude that  at  high  temperatures,  also,  the  conduction  of 
electricity  through  copper  oxide  is  not  accompanied  by 
electrolysis. 
Sodium  Peroxide. 
The  results  obtained  with  this  oxide  were  not  very  satis- 
factory on  account  of  the  readiness  with  which  it  deliquesces 
when  exposed  to  air.  Only  a  small  range  of  temperature 
could  be  used,  as  the  oxide  melts  at  about  300°  0.  The 
numbers  in  the  following  table  refer  to  a  piece  of  oxide  1  sq. 
cm.  in  area  and  2  mms.  thick. 
Temperature 
Centigrade. 
Resistance  in 
ohms. 
Conductivity  in 
mhos. 
20 
5000 
4   X10-5 
59 
2500 
8   Xl0~° 
109 
1200 
1-67X10-4 
198 
600 
3-3   X10~4 
244 
400 
5-0   Xl0-4 
284 
200 
1-0  xio~3 
Diagram  VIII. 
0  100°       200°  500'        400" 
The  above  values  of  the  conductivity  are  plotted  again-1 
the  corresponding  temperatures  in  diagram  VIII. 
2  M  2 
