﻿124: 
  Mr. 
  S. 
  Kinoshita 
  on 
  Condensation 
  of 
  

  

  X 
  being 
  tbe 
  radioactive 
  constant 
  of 
  the 
  emanation. 
  Let 
  

   s 
  T 
  and 
  s 
  be 
  the 
  values 
  of 
  s 
  at 
  t 
  = 
  r 
  and 
  2 
  = 
  respectively, 
  

   then 
  by 
  integration 
  

  

  or 
  r 
  k\(s 
  r 
  — 
  s 
  ) 
  

  

  l—e- 
  KT 
  

  

  It= 
  

  

  The 
  experiment 
  therefore 
  simply 
  consists 
  in 
  measuring 
  the 
  

   number 
  of 
  scale-divisions 
  passed 
  over 
  in 
  a 
  constant 
  interval 
  

   of 
  time 
  t. 
  This 
  number 
  is 
  proportional 
  to 
  the 
  activity, 
  

   L 
  £., 
  to 
  the 
  amount 
  of 
  emanation 
  escaping 
  with 
  the 
  gas. 
  A 
  

   correction 
  must 
  be 
  applied 
  for 
  the 
  active 
  deposit 
  which 
  is 
  

   formed 
  from 
  the 
  emanation. 
  

  

  As 
  a 
  verification 
  of 
  the 
  method, 
  the 
  radioactive 
  constant 
  of 
  

   the 
  actinium 
  emanation 
  was 
  determined 
  by 
  measuring 
  s 
  T 
  — 
  s 
  

   for 
  T= 
  25 
  and 
  20 
  seconds. 
  The 
  results 
  are 
  as 
  follows 
  : 
  — 
  

  

  T 
  = 
  25 
  seconds. 
  

   3-6 
  

   3-6 
  

   3-6 
  

  

  Mean... 
  3 
  . 
  6 
  

  

  T 
  = 
  20 
  seconds. 
  

   8-7 
  

   8-73 
  

   8-64 
  

   8-75 
  

   Mean... 
  8 
  . 
  705 
  

  

  8-705 
  

  

  This 
  gives 
  X==.j-log« 
  8 
  '« 
  =0*176 
  or 
  period=3*92 
  seconds? 
  

   which 
  agrees 
  very 
  well 
  with 
  previous 
  determinations. 
  

  

  Experiment 
  with 
  Actinium 
  Emanation. 
  

  

  The 
  copper 
  spiral 
  was 
  immersed 
  in 
  a 
  Dewar's 
  vessel, 
  the 
  

   mouth 
  of 
  which 
  was 
  closed 
  with 
  cotton-wool, 
  and 
  when 
  the 
  

   spiral 
  had 
  cooled 
  down, 
  all 
  the 
  liquid 
  air 
  was 
  removed 
  by 
  

   inverting 
  the 
  vessel, 
  after 
  which 
  the 
  temperature 
  was 
  allowed 
  

   to 
  rise. 
  The 
  rate 
  of 
  rise 
  of 
  temperature 
  was 
  about 
  1°"1 
  to 
  

   1°*3 
  per 
  minute. 
  The 
  electroscope 
  and 
  the 
  spiral 
  were 
  

   evacuated 
  by 
  a 
  water-pump 
  to 
  a 
  pressure 
  of 
  10 
  mm. 
  of 
  

   mercury, 
  then 
  all 
  the 
  stopcocks 
  C,. 
  C 
  2 
  , 
  C 
  s 
  , 
  and 
  C 
  4 
  were 
  

   closed, 
  A 
  being 
  at 
  atmospheric 
  pressure. 
  C 
  2 
  was 
  then 
  

   opened, 
  the 
  gas 
  in 
  A 
  which 
  conveyed 
  the 
  emanation 
  rushed 
  

   into 
  the 
  spiral 
  ; 
  and 
  after 
  a 
  few 
  seconds 
  G 
  a 
  was 
  again 
  closed. 
  

   Seventeen 
  seconds 
  after 
  G$ 
  had 
  been 
  opened, 
  the 
  stopcock 
  C 
  3 
  

   was 
  turned; 
  when 
  the 
  gas 
  rushed 
  into 
  the 
  electroscope, 
  and 
  

   the 
  gold-leaf 
  began 
  suddenly 
  to 
  fall. 
  Two 
  readings 
  S 
  and 
  

   s 
  T 
  were 
  taken, 
  the 
  former 
  just 
  before 
  opening 
  Cj 
  and 
  the 
  

   latter 
  alter 
  20 
  seconds. 
  Act. 
  A 
  was 
  deposited 
  rapidly 
  on 
  

  

  