﻿the 
  Electromotive 
  Force 
  of 
  Clark 
  Cells 
  with 
  Temperature. 
  295 
  

  

  two 
  serious 
  drawbacks, 
  firstly, 
  an 
  error 
  of 
  a 
  few 
  tenths 
  of 
  a 
  

   degree 
  in 
  the 
  temperature 
  at 
  which 
  the 
  cell 
  is 
  saturated 
  makes 
  

   an 
  error 
  of 
  several 
  ten-thousandths 
  of 
  a 
  volt 
  in 
  the 
  E.M.F., 
  

   and, 
  secondly, 
  every 
  time 
  a 
  current 
  passes 
  through 
  the 
  cell 
  a 
  

   certain 
  amount 
  of 
  zinc 
  is 
  dissolved, 
  so 
  in 
  time 
  the 
  solution 
  

   becomes 
  stronger. 
  This 
  point 
  is 
  of 
  particular 
  importance 
  

   where 
  the 
  cells 
  are 
  used 
  with 
  condensers. 
  

  

  Fig. 
  5. 
  — 
  Curves 
  connecting 
  E.M.F. 
  and 
  Temperature. 
  Kate 
  of 
  Variation 
  of 
  Temperature, 
  

  

  1° 
  in 
  15 
  minutes. 
  

  

  Temperature 
  in 
  degrees 
  Centigrade. 
  

   16 
  17 
  18 
  19 
  20 
  

  

  21 
  

  

  22 
  

  

  