﻿70 
  JOURNAL 
  OF 
  THE 
  WASHINGTON 
  ACADEMY 
  OF 
  SCIENCES 
  VOL. 
  12, 
  NO. 
  3 
  

  

  marked 
  under-cooling 
  of 
  the 
  electrolyte 
  before 
  freezing 
  began. 
  The 
  

   dry 
  cell 
  showed 
  a 
  considerable 
  increase 
  in 
  voltage 
  at 
  — 
  112° 
  C. 
  over 
  the 
  

   normal 
  value. 
  The 
  most 
  remarkable 
  facts 
  are 
  the 
  reversal 
  of 
  voltages 
  

   and 
  the 
  extraordinarily 
  large 
  values 
  of 
  voltage 
  exhibited 
  by 
  the 
  stor- 
  

   age 
  cell, 
  exceeding 
  ten 
  volts 
  at 
  the 
  lowest 
  temperatures. 
  The 
  cur- 
  

   rent 
  was 
  of 
  course 
  vanishingly 
  small. 
  

  

  Nernst's 
  equation 
  applied 
  to 
  the 
  storage 
  battery 
  in 
  accordance 
  with 
  

   Liebenow's 
  theory^ 
  is 
  as 
  follows: 
  

  

  ^ 
  RT 
  ^ 
  ex. 
  

  

  E 
  = 
  In 
  

  

  [Pb++][PbO— 
  ] 
  

  

  where 
  Cp 
  and 
  C^ 
  are 
  the 
  solution 
  tensions 
  of 
  the 
  positive 
  and 
  nega- 
  

   tive 
  active 
  material 
  and 
  the 
  bracketed 
  values 
  represent 
  the 
  corre- 
  

   sponding 
  ionic 
  concentrations. 
  It 
  is 
  evident 
  that 
  a 
  decrease 
  in 
  the 
  

   ionic 
  concentrations 
  would 
  result 
  in 
  an 
  increase 
  in 
  the 
  value 
  of 
  E 
  if 
  

   other 
  quantities 
  remained 
  the 
  same. 
  

  

  The 
  freezing 
  of 
  the 
  electrolyte 
  reduces 
  the 
  mobility 
  of 
  the 
  ions 
  

   practically 
  to 
  zero. 
  If, 
  then, 
  the 
  ions 
  which 
  are 
  in 
  immediate 
  contact 
  

   with 
  the 
  surface 
  of 
  the 
  electrodes 
  are 
  discharged, 
  they 
  cannot 
  be 
  re- 
  

   placed 
  by 
  the 
  migration 
  of 
  other 
  ions 
  from 
  the 
  electrolyte 
  and 
  the 
  effect 
  

   in 
  the 
  region 
  of 
  the 
  electrodes 
  is 
  essentially 
  a 
  decrease 
  in 
  the 
  ionic 
  con- 
  

   centrations. 
  The 
  equation 
  therefore 
  suggests 
  the 
  possibility 
  of 
  in- 
  

   creased 
  values 
  of 
  B 
  as 
  was 
  observed 
  after 
  the 
  freezing 
  occurred. 
  

  

  No 
  ready 
  explanation 
  of 
  the 
  reversal 
  of 
  voltage 
  is 
  available 
  unless 
  

   it 
  be 
  assumed 
  that 
  the 
  variation 
  of 
  solution 
  tension 
  of 
  each 
  electrode 
  

   with 
  temperature 
  is 
  such 
  that 
  curves 
  representing 
  them 
  would 
  inter- 
  

   sect 
  at 
  the 
  temperature 
  at 
  which 
  reversal 
  occurs. 
  Pressure 
  may 
  have 
  

   had 
  something 
  to 
  do 
  with 
  the 
  voltage 
  variations 
  since 
  the 
  electrom- 
  

   eter 
  showed 
  violent 
  fluctuations 
  whenever 
  the 
  frozen 
  electrolyte 
  of 
  

   the 
  storage 
  cell 
  "ticketed." 
  Ice 
  below 
  the 
  freezing 
  temperature 
  

   sometimes 
  makes 
  a 
  similar 
  ticking 
  sound. 
  

  

  The 
  genuineness 
  of 
  the 
  reversed 
  voltage 
  was 
  shown 
  by 
  the 
  following 
  

   observations 
  : 
  The 
  dry 
  cell 
  after 
  showing 
  a 
  steady 
  reversed 
  voltage 
  of 
  

   about 
  1.4 
  volts 
  was 
  removed 
  from 
  the 
  liquid 
  air 
  and 
  in 
  the 
  course 
  of 
  

   a 
  few 
  minutes, 
  the 
  reversed 
  voltage 
  decreased 
  steadily, 
  passed 
  through 
  

   zero, 
  and 
  increased 
  to 
  a 
  normal 
  positive 
  value. 
  Secondly, 
  the 
  po- 
  

   tentiometer 
  used 
  for 
  simultaneous 
  measurements 
  with 
  the 
  electrom- 
  

   eter 
  on 
  the 
  storage 
  cell 
  retained 
  enough 
  sensibility 
  to 
  show 
  that 
  the 
  

  

  ^ 
  Zeitschr. 
  f. 
  Elektrochem. 
  3: 
  625. 
  1897. 
  

  

  