﻿358 
  Messrs. 
  E. 
  Marsden 
  and 
  R. 
  H. 
  Wilson 
  on 
  some 
  

  

  This 
  agreement 
  between 
  the 
  periods, 
  which 
  was 
  verified 
  in 
  

   several 
  sets 
  of 
  observations, 
  is 
  very 
  remarkable 
  if 
  C 
  a 
  and 
  

   C/3 
  have 
  an 
  independent 
  existence 
  as 
  different 
  products, 
  and 
  

   is 
  therefore 
  strong 
  evidence 
  against 
  that 
  hypothesis. 
  

  

  Experiments 
  were 
  tried 
  in 
  which, 
  before 
  dipping 
  in 
  the 
  

   nickel 
  plate, 
  a 
  few 
  drops 
  of 
  stannous 
  chloride 
  were 
  added 
  to 
  

   the 
  solution 
  of 
  the 
  active 
  deposit. 
  Even 
  in 
  this 
  case 
  no 
  

   change 
  of 
  balance 
  with 
  decay 
  could 
  be 
  observed, 
  and, 
  more- 
  

   over, 
  keeping 
  the 
  electrodes 
  in 
  the 
  same 
  positions 
  as 
  before, 
  

   the 
  position 
  of 
  the 
  source 
  S 
  for 
  a 
  balance 
  was 
  exactly 
  the 
  

   same. 
  As 
  the 
  balance 
  was 
  very 
  sensitive 
  to 
  changes 
  in 
  the 
  

   position 
  of 
  S, 
  this 
  result 
  shows 
  that 
  the 
  proportion 
  of 
  the 
  pro- 
  

   ducts 
  on 
  the 
  nickel 
  plate 
  was 
  exactly 
  the 
  same 
  as 
  when 
  no 
  

   stannous 
  chloride 
  was 
  used. 
  

  

  Since 
  this 
  result 
  is 
  practically 
  in 
  direct 
  opposition 
  to 
  the 
  

   conclusion 
  of 
  Miss 
  Meitner, 
  a 
  repetition 
  of 
  her 
  experiments 
  

   was 
  undertaken. 
  A 
  hydrochloric 
  acid 
  solution 
  of 
  the 
  active 
  

   deposit 
  was 
  made, 
  and, 
  maintaining 
  the 
  temperature 
  at 
  about 
  

   90° 
  C, 
  seven 
  successive 
  well-polished 
  nickel 
  plates 
  were 
  

   immersed 
  for 
  a 
  period 
  of 
  twenty 
  minutes 
  in 
  all. 
  In 
  this 
  way 
  

   the 
  C 
  product 
  was 
  nearly 
  all 
  removed 
  and 
  the 
  D 
  allowed 
  to 
  

   decay. 
  A 
  drop 
  of 
  the 
  solution 
  was 
  taken 
  and 
  evaporated 
  on 
  

   either 
  a 
  platinum 
  foil 
  or 
  a 
  watch-glass 
  for 
  observations 
  by 
  

   a, 
  rays, 
  and 
  the 
  remainder 
  was 
  quickly 
  boiled 
  to 
  dryness 
  for 
  

   observations 
  by 
  y 
  rays. 
  

  

  In 
  the 
  earlier 
  experiments 
  results 
  were 
  obtained 
  exactly 
  

   the 
  same 
  as 
  those 
  of 
  Miss 
  Meitner, 
  i. 
  e. 
  the 
  7 
  and 
  a 
  ray 
  

   activities 
  rose 
  proportionately, 
  while 
  when 
  stannous 
  chloride 
  

   was 
  added 
  the 
  7-ray 
  activity 
  rose 
  from 
  a 
  lower 
  initial 
  per- 
  

   centage 
  value 
  than 
  the 
  a-ray 
  activity 
  (see 
  fig. 
  1). 
  

  

  Further 
  investigation 
  has, 
  however, 
  led 
  us 
  to 
  the 
  con- 
  

   viction 
  that 
  the 
  results 
  are 
  anomalous, 
  and 
  caused 
  mainly 
  by 
  

   the 
  fact 
  that 
  in 
  presence 
  of 
  hydrochloric 
  acid 
  thorium 
  G 
  

   volatilizes 
  at 
  a 
  comparatively 
  low 
  temperature. 
  In 
  the 
  

   ordinary 
  case 
  of 
  a 
  plate 
  exposed 
  in 
  air 
  to 
  thorium 
  emanation, 
  

   when 
  presumably 
  the 
  products 
  are 
  present 
  as 
  oxides, 
  B 
  is 
  

   volatile 
  at 
  700° 
  0. 
  * 
  and 
  C 
  at 
  1200°C. 
  If 
  a 
  hydrochloric 
  

   acid 
  solution 
  of 
  the 
  active 
  deposit 
  is 
  taken 
  and 
  boiled 
  to 
  

   dryness 
  on 
  a 
  watch-glass 
  and 
  heated 
  gently 
  for 
  about 
  one 
  

   minute, 
  we 
  find 
  from 
  the 
  subsequent 
  variation 
  in 
  activity 
  

   with 
  time 
  that 
  about 
  30 
  per 
  cent, 
  of 
  the 
  C 
  is 
  removed 
  and 
  

   practically 
  none 
  of 
  the 
  B. 
  With 
  a 
  nitric 
  acid 
  solution, 
  

   however, 
  even 
  with 
  strong 
  heating 
  neither 
  product 
  is 
  

   volatilized. 
  If 
  the 
  hydrochloric 
  acid 
  solution 
  be 
  taken, 
  and 
  

  

  * 
  Miss 
  Slater, 
  Phil. 
  Mag. 
  ix. 
  p. 
  628 
  (1905). 
  

  

  