﻿66 
  JOURNAL 
  OF 
  THE 
  WASHINGTON 
  ACADEMY 
  OF 
  SCIENCES 
  VOI^. 
  12, 
  NO. 
  3 
  

  

  circuit 
  voltages 
  as 
  measured 
  for 
  two 
  different 
  cells 
  by 
  the 
  electrom- 
  

   eter 
  and 
  the 
  potentiometer. 
  Curves 
  C, 
  D, 
  E 
  and 
  F 
  represent 
  the 
  

   terminal 
  voltage 
  when 
  the 
  cells 
  were 
  discharging 
  through 
  25,000, 
  

   100, 
  25 
  and 
  4 
  ohms, 
  respectively. 
  The 
  curves 
  indicate 
  the 
  existence 
  of 
  

   a 
  critical 
  point 
  at 
  about 
  —21° 
  C. 
  

  

  The 
  open-circuit 
  voltage 
  curves 
  indicate 
  that 
  changes 
  in 
  the 
  temper- 
  

   ature 
  coefficient 
  occur 
  at 
  certain 
  temperatures. 
  Between 
  +26° 
  and 
  

   0° 
  C. 
  the 
  coefficient 
  was 
  found 
  to 
  be 
  constant 
  and 
  somewhat 
  less 
  than 
  

   a 
  millivolt 
  per 
  degree. 
  The 
  coefficient 
  is 
  positive, 
  that 
  is, 
  increase 
  

   in 
  temperature 
  is 
  accompanied 
  by 
  increase 
  in 
  voltage. 
  Between 
  0° 
  

  

  TerTjocrK/Zar-G. 
  c/efir^as 
  Ce/^;^5<^-oofe> 
  

  

  Fig. 
  1. 
  Effect 
  of 
  temperature 
  on 
  the 
  voltage 
  of 
  dry 
  cells. 
  

  

  and 
  -20° 
  C. 
  the 
  coefficient 
  is 
  still 
  positive, 
  but 
  larger. 
  At 
  -20.4° 
  C. 
  

   a 
  break 
  occurs. 
  The 
  temperature 
  coefficient 
  becomes 
  much 
  larger 
  

   during 
  the 
  next 
  few 
  degrees 
  and 
  then 
  changes 
  to 
  negative 
  at 
  about 
  

   — 
  24°. 
  At 
  —54° 
  the 
  coefficient 
  again 
  becomes 
  positive. 
  It 
  is 
  inter- 
  

   esting 
  to 
  note 
  that 
  at 
  — 
  54° 
  C. 
  the 
  voltage 
  is 
  higher 
  than 
  at 
  ordinary 
  

   temperatures. 
  

  

  Curves 
  C, 
  D, 
  E 
  and 
  F 
  show 
  that 
  the 
  ordinary 
  dry 
  cell 
  can 
  deliver 
  

   current 
  down 
  to 
  about 
  —20° 
  C, 
  below 
  which 
  the 
  voltage 
  falls 
  off 
  

   rapidly 
  to 
  zero. 
  

  

  