﻿the 
  Ions 
  of 
  Gases. 
  369 
  

  

  their 
  expressions 
  are 
  not 
  the 
  right 
  ones 
  for 
  the 
  purpose 
  to 
  

   \Yhich 
  they 
  apply 
  them. 
  For 
  example 
  J. 
  J. 
  Thomson 
  writes 
  

   e?l21^a 
  for 
  the 
  electrical 
  potential 
  energy 
  of 
  an 
  electrified 
  

   drop 
  of 
  radius 
  a 
  surrounded 
  by 
  a 
  medium 
  of 
  dielectric 
  

   capacity 
  K, 
  which 
  is 
  put 
  =1, 
  and 
  Langeyin 
  also 
  uses 
  e^l2a. 
  

   They 
  then 
  apply 
  this 
  to 
  an 
  electron 
  surrounded 
  by 
  water. 
  

   But, 
  unless 
  the 
  electron 
  spreads 
  itself 
  oyer 
  the 
  surface 
  of 
  the 
  

   drop 
  in 
  much 
  the 
  same 
  way 
  as 
  a 
  large 
  number 
  of 
  like 
  electrons 
  

   would, 
  this 
  expression 
  is 
  no 
  longer 
  yalid. 
  The 
  electrical 
  

   energy 
  of 
  an 
  electron 
  and 
  an 
  envelope 
  of 
  molecules 
  is 
  a 
  

   mutual 
  affair, 
  tending 
  to 
  take 
  the 
  form 
  e^s/a^ 
  for 
  a 
  central 
  

   electron 
  and 
  a 
  molecule 
  at 
  distance 
  a, 
  so 
  the 
  total 
  electric 
  

   energy 
  of 
  electron 
  and 
  drop 
  must 
  be 
  expressed 
  by 
  a 
  form 
  

   quite 
  different 
  from 
  the 
  e^l2a 
  used 
  by 
  both 
  authors. 
  Then 
  

   again 
  they 
  carry 
  the 
  conception 
  of 
  surface 
  tension 
  and 
  

   surface 
  energy 
  even 
  into 
  the 
  dynamical 
  specification 
  of 
  the 
  

   smallest 
  drops. 
  The 
  directive 
  effect 
  of 
  the 
  central 
  electron 
  

   on 
  the 
  few 
  molecules 
  of 
  the 
  smallest 
  drop 
  must 
  profoundly 
  

   modify 
  their 
  cohesional 
  forces. 
  For 
  these 
  reasons 
  the 
  theory 
  

   of 
  Thomson 
  and 
  Langevin 
  appears 
  to 
  me 
  to 
  be 
  quite 
  illusory 
  

   in 
  its 
  details 
  and 
  to 
  give 
  its 
  remarkable 
  result 
  concerning 
  

   fourfold 
  saturation 
  by 
  a 
  concealed 
  compensation 
  of 
  errors. 
  

   They 
  give 
  a 
  theory 
  of 
  what 
  is 
  essentially 
  a 
  molecular 
  affair 
  

   by 
  means 
  of 
  purely 
  molar 
  considerations 
  and 
  data. 
  Their 
  

   theory 
  applies 
  to 
  drops 
  which 
  are 
  large 
  enough 
  to 
  have 
  a 
  

   surface 
  tension 
  like 
  that 
  of 
  ordinary 
  water 
  and 
  which 
  carry 
  a 
  

   surface 
  charge 
  of 
  electricity. 
  It 
  can 
  give 
  no 
  account 
  of 
  the 
  

   real 
  happenings 
  when 
  vapour 
  of 
  water 
  begins 
  to 
  gather 
  round 
  

   a 
  small 
  ion. 
  

  

  SUMMAEY. 
  

  

  In 
  a 
  dynamical 
  theory 
  of 
  the 
  ions 
  of 
  gases 
  the 
  two 
  new 
  

   types 
  of 
  viscosity 
  previously 
  investigated 
  for 
  ions 
  in 
  electro- 
  

   lytic 
  solutions 
  are 
  found 
  to 
  be 
  of 
  paramount 
  importance. 
  The 
  

   induced 
  viscosity, 
  namely 
  that 
  which 
  arises 
  from 
  the 
  electric 
  

   action 
  of 
  the 
  ion 
  upon 
  surrounding 
  molecules, 
  produces 
  in 
  all 
  

   gases 
  about 
  7*6 
  times 
  as 
  much 
  resistance 
  to 
  the 
  motion 
  of 
  the 
  

   small 
  ion 
  as 
  ordinary 
  gaseous 
  viscosity 
  does. 
  The 
  other 
  type 
  

   of 
  viscosity, 
  namely 
  that 
  which 
  arises 
  from 
  the 
  mutual 
  energy 
  

   of 
  oppositely 
  charged 
  ions, 
  is 
  not 
  of 
  large 
  enough 
  amount 
  to 
  

   make 
  its 
  appearance 
  in 
  the 
  experimental 
  study 
  of 
  small 
  ions 
  

   at 
  the 
  low 
  concentrations 
  in 
  which 
  these 
  are 
  usually 
  employed. 
  

   In 
  the 
  case 
  of 
  the 
  small 
  ion 
  there 
  is 
  another 
  result 
  of 
  the 
  

   electric 
  action 
  between 
  it 
  and 
  surrounding 
  molecules, 
  for 
  this 
  

   causes 
  collisions 
  to 
  occur 
  more 
  frequently, 
  as 
  cohesional 
  force 
  

   does 
  in 
  the 
  theory 
  of 
  the 
  effect 
  of 
  temperature 
  on 
  the 
  viscosity 
  

  

  