﻿FEB. 
  4, 
  1922 
  VINAL 
  AND 
  ALTRUP: 
  CELLS 
  AT 
  LOW 
  TEMPERATURES 
  65 
  

  

  lowest 
  temperature 
  attainable 
  by 
  this 
  means 
  was 
  reached, 
  when 
  an 
  

   excess 
  of 
  the 
  snow 
  was 
  packed 
  around 
  the 
  cells. 
  For 
  the 
  range 
  

   + 
  20 
  ° 
  C 
  . 
  to 
  — 
  1 
  70 
  ° 
  C 
  . 
  liquid 
  air 
  was 
  used 
  for 
  cooling 
  . 
  The 
  dry 
  cells 
  were 
  

   placed 
  in 
  a 
  double 
  walled 
  glass 
  jacket 
  similar 
  to 
  a 
  Dewar 
  vessel, 
  

   but 
  having 
  air 
  at 
  atmospheric 
  pressure 
  between 
  the 
  walls. 
  This 
  was 
  

   submerged 
  in 
  liquid 
  air 
  contained 
  in 
  a 
  larger 
  Dewar 
  flask. 
  The 
  stor- 
  

   age 
  cell, 
  contained 
  in 
  a 
  glass 
  test 
  tube, 
  was 
  similarly 
  arranged 
  with 
  the 
  

   addition 
  of 
  a 
  ground-cork 
  packing 
  to 
  protect 
  it 
  from 
  breakage. 
  By 
  

   this 
  means 
  the 
  cooling 
  was 
  gradual, 
  about 
  2 
  hours 
  being 
  required 
  for 
  

   the 
  cells 
  to 
  fall 
  from 
  room 
  temperature 
  to 
  the 
  lowest 
  temperature 
  

   available. 
  

  

  The 
  temperature 
  was 
  measured 
  by 
  a 
  thermocouple 
  of 
  standardized 
  

   constantan 
  and 
  copper 
  wire. 
  Since 
  it 
  was 
  not 
  practicable 
  to 
  insert 
  

   the 
  thermocouple 
  in 
  the 
  dry 
  cells 
  of 
  which 
  the 
  e.m.f. 
  was 
  measured, 
  

   the 
  thermocouple 
  was 
  placed 
  at 
  the 
  center 
  of 
  a 
  similar 
  dry 
  cell 
  which 
  

   was 
  grouped 
  symmetrically 
  with 
  the 
  other 
  cells. 
  The 
  temperature 
  

   of 
  the 
  storage 
  cell 
  was 
  measured 
  by 
  placing 
  the 
  thermocouple, 
  protected 
  

   by 
  a 
  thin-walled 
  glass 
  tube, 
  in 
  the 
  electrolyte 
  between 
  the 
  positive 
  and 
  

   negative 
  plates 
  of 
  the 
  cell. 
  The 
  electromotive 
  forces 
  of 
  the 
  thermocou- 
  

   ples 
  were 
  read 
  on 
  a 
  high 
  resistance 
  potentiometer. 
  

  

  The 
  dry 
  cells 
  measured 
  were 
  "^ 
  I 
  ^ 
  inch 
  diameter 
  X 
  ^2} 
  1% 
  inch 
  high, 
  

   taken 
  from 
  flashlight 
  batteries 
  of 
  a 
  well 
  known 
  make. 
  A 
  few 
  experi- 
  

   ments 
  on 
  silver 
  chloride 
  dry 
  cells 
  were 
  made 
  also. 
  The 
  storage 
  cells 
  

   were 
  made 
  by 
  cutting 
  strips 
  of 
  suitable 
  size 
  from 
  the 
  pasted 
  plates 
  of 
  

   an 
  automobile 
  starting 
  and 
  lighting 
  battery. 
  These 
  were 
  placed 
  in 
  

   test 
  tubes 
  about 
  1 
  inch 
  in 
  diameter 
  with 
  perforated 
  hard 
  rubber 
  sep- 
  

   arators 
  and 
  a 
  few 
  glass 
  beads. 
  The 
  electrolyte 
  was 
  adjusted 
  to 
  a 
  spe- 
  

   cific 
  gravity 
  of 
  1.275 
  to 
  1.280 
  at 
  the 
  end 
  of 
  5 
  days 
  of 
  continuous 
  charg- 
  

   ing 
  at 
  0.4 
  ampere. 
  

  

  The 
  voltage 
  of 
  the 
  cells 
  during 
  test 
  was 
  measured 
  by 
  3 
  different 
  

   methods 
  but 
  the 
  open-circuit 
  measurements 
  at 
  the 
  lowest 
  tempera- 
  

   tures 
  could 
  be 
  made 
  only 
  by 
  an 
  electrometer. 
  This 
  instrument 
  was 
  

   loaned 
  to 
  us 
  by 
  the 
  Department 
  of 
  Terrestrial 
  Magnetism. 
  The 
  open 
  

   circuit 
  voltages 
  were 
  also 
  measured 
  on 
  a 
  20,000-ohm 
  potentiometer 
  

   which 
  afforded 
  a 
  very 
  sensitive 
  method 
  before 
  the 
  cells 
  were 
  frozen 
  

   although 
  after 
  this 
  it 
  was 
  nearly 
  useless. 
  A 
  voltmeter 
  having 
  a 
  scale 
  

   of 
  2.5 
  volts 
  and 
  a 
  resistance 
  of 
  25,000 
  ohms 
  was 
  used 
  for 
  some 
  of 
  the 
  

   measurements. 
  

  

  The 
  results 
  of 
  experiments 
  with 
  dry 
  cells 
  of 
  the 
  ordinary 
  type 
  are 
  

   shown 
  in 
  Table 
  1 
  and 
  Fig. 
  1. 
  Curves 
  A 
  and 
  B 
  represent 
  the 
  open- 
  

  

  