﻿of 
  Radium 
  in 
  an 
  Electric 
  Field. 
  317 
  

  

  a 
  quantity 
  of 
  carnotite. 
  or 
  in 
  some 
  cases 
  from 
  an 
  aqueous 
  solu- 
  

   tion 
  of 
  a 
  radium 
  salt, 
  was 
  passed 
  into 
  the 
  containing 
  vessel 
  and 
  

   remained 
  there 
  under 
  the 
  desired 
  conditions 
  of 
  potential, 
  pres- 
  

   sure, 
  etc.. 
  until 
  radio-active 
  equilibrium 
  was 
  established 
  ; 
  in 
  

   general 
  this 
  period 
  was 
  about 
  3 
  hours. 
  The 
  emanation 
  was 
  

   blown 
  out 
  by 
  means 
  of 
  a 
  strong 
  current 
  of 
  air 
  from 
  a 
  force- 
  

   pump, 
  and 
  the 
  ebonite 
  plug 
  containing 
  the 
  central 
  electrode 
  

   was 
  then 
  removed. 
  A 
  fresh 
  electrode 
  was 
  suspended 
  in 
  the 
  

   vessel 
  and 
  the 
  ionization 
  current 
  due 
  to 
  the 
  ' 
  case 
  ' 
  activity 
  was 
  

   measured 
  at 
  10 
  and 
  15 
  minutes 
  after 
  the 
  emanation 
  had 
  been 
  

   removed 
  ; 
  the 
  activity 
  on 
  the 
  central 
  electrode 
  was 
  measured 
  

   by 
  suspending 
  it 
  in 
  a 
  vessel 
  of 
  construction 
  identical 
  with 
  that 
  

   which 
  contained 
  the 
  emanation 
  and 
  observing 
  the 
  ionization 
  

   current 
  at 
  20 
  and 
  25 
  minutes 
  after 
  the 
  emanation 
  had 
  been 
  

   removed. 
  The 
  activity 
  when 
  in 
  equilibrium 
  with 
  the 
  ema- 
  

   nation 
  was 
  then 
  calculated 
  in 
  the 
  usual 
  manner. 
  

  

  The 
  diagram 
  of 
  connections 
  is 
  the 
  same 
  as 
  that 
  given 
  in 
  the 
  

   previous 
  paper 
  and 
  is 
  reproduced 
  in 
  fig. 
  1 
  ; 
  in 
  the 
  present 
  

   investigation 
  R 
  and 
  R' 
  were 
  wire 
  resistances 
  of 
  50,000 
  and 
  

   100,000 
  ohms 
  respectively. 
  The 
  Dolezalek 
  electrometer 
  had 
  a 
  

   platinum 
  suspension, 
  and 
  with 
  120 
  volts 
  on 
  the 
  needle 
  the 
  sen- 
  

   sitiveness 
  was 
  180 
  mm 
  per 
  volt. 
  C 
  and 
  B 
  represent 
  capacities 
  

   which 
  could 
  be 
  added 
  to 
  the 
  system 
  by 
  means 
  of 
  the 
  key 
  K, 
  

   and 
  the 
  total 
  capacity 
  of 
  the 
  system 
  was 
  then 
  increased 
  21 
  

   times. 
  A 
  potentiometer 
  device, 
  not 
  shown 
  in 
  the 
  diagram, 
  was 
  

   employed 
  when 
  measurements 
  of 
  the 
  ionization 
  current- 
  were 
  

   made 
  : 
  this 
  device 
  enabled 
  the 
  range 
  of 
  swing 
  of 
  the 
  electrom- 
  

   eter 
  needle 
  to 
  be 
  so 
  adjusted 
  that 
  its 
  mid-point 
  coincided 
  with 
  

   the 
  zero 
  of 
  the 
  instrument, 
  a 
  precaution 
  which 
  was 
  especially 
  

   necessary, 
  when 
  the 
  applied 
  potential 
  was 
  small. 
  Reference 
  

   should 
  be 
  made 
  to 
  the 
  previous 
  paper 
  for 
  a 
  more 
  detailed 
  

   account 
  of 
  the 
  apparatus 
  and 
  method 
  of 
  procedure. 
  

  

  Experiments 
  xoith 
  a 
  Cylindrical 
  Condenser 
  of 
  small 
  diameter. 
  

  

  3. 
  In 
  the 
  previous 
  experiments 
  the 
  greatest 
  amount 
  of 
  active 
  

   deposit 
  that 
  settled 
  on 
  the 
  cathode 
  was 
  about 
  90 
  per 
  cent 
  of 
  the 
  

   total 
  ; 
  this 
  occurred 
  for 
  a 
  potential 
  of 
  4000 
  volts. 
  It 
  was 
  of 
  

   interest 
  to 
  ascertain 
  the 
  effect 
  of 
  applying 
  a 
  large 
  potential 
  

   across 
  a 
  smaller 
  distance 
  so 
  as 
  to 
  obtain 
  very 
  large 
  values 
  for 
  

   the 
  electric 
  field. 
  For 
  this 
  purpose 
  two 
  cylindrical 
  vessels 
  

   were 
  constructed 
  of 
  the 
  following 
  dimensions 
  : 
  

  

  Height 
  140 
  mra 
  

  

  Inner 
  diameter 
  19 
  

  

  Length 
  of 
  central 
  electrode 
  101 
  

  

  Radium 
  emanation 
  mixed 
  with 
  air 
  at 
  1 
  atmosphere 
  pressure 
  

   was 
  introduced 
  into 
  one 
  of 
  these 
  vessels, 
  and 
  when 
  a 
  positive 
  

   potential 
  of 
  3000 
  volts 
  was 
  applied 
  to 
  the 
  case 
  it 
  was 
  found 
  

  

  