﻿122 
  Mr. 
  S. 
  Kinoshita 
  on 
  Condensation 
  of 
  

  

  can 
  be 
  measured. 
  After 
  leaving 
  it 
  for 
  a 
  certain 
  time 
  in 
  this 
  

   spiral 
  to 
  attain 
  its 
  temperature, 
  and 
  to 
  let 
  the 
  emanation 
  

   condense 
  on 
  the 
  walls 
  of 
  the 
  spiral, 
  the 
  gas 
  is 
  quickly 
  led 
  

   into 
  a 
  partially 
  evacuated 
  emanation 
  electroscope, 
  by 
  means 
  

   of 
  which 
  the 
  activity 
  of 
  the 
  emanation, 
  escaping 
  uncondensed 
  

   along 
  with 
  the 
  gas, 
  can 
  be 
  measured. 
  

  

  The 
  actinium 
  emanation 
  loses 
  its 
  activity 
  very 
  rapid 
  1\% 
  

   its 
  period 
  being 
  only 
  3*9 
  seconds, 
  so 
  that 
  the 
  activity 
  

   decreases 
  to 
  7 
  per 
  cent, 
  of 
  its 
  initial 
  value 
  after 
  15 
  second 
  s, 
  

   and 
  to 
  0*5 
  per 
  cent, 
  after 
  30 
  seconds. 
  To 
  get 
  measurable 
  

   effects 
  it 
  was, 
  therefore, 
  practically 
  impossible 
  to 
  leave 
  the 
  

   emanation 
  for 
  more 
  than 
  30 
  seconds 
  to 
  cool, 
  although 
  

   1*5 
  grammes 
  of 
  actinium 
  preparation 
  had 
  been 
  taken, 
  the 
  

   activity 
  of 
  which 
  was 
  about 
  6000 
  times 
  that 
  of 
  uranium 
  oxide. 
  

   It 
  was, 
  however, 
  found 
  experimentally 
  that 
  the 
  proportion 
  

   of 
  uncondensed 
  emanation 
  at 
  a 
  given 
  temperature 
  is 
  the 
  

   same 
  whether 
  the 
  emanation 
  is 
  left 
  in 
  the 
  spiral 
  for 
  15 
  or 
  

   24 
  seconds, 
  provided 
  the 
  pressure 
  is 
  the 
  same 
  in 
  both 
  cases. 
  

   Consequently 
  15 
  seconds 
  seems 
  sufficient 
  time 
  to 
  allow 
  for 
  

   condensation 
  in 
  the 
  spiral 
  employed. 
  At 
  a 
  temperature 
  a 
  

   few 
  degrees 
  below 
  that 
  of 
  complete 
  condensation, 
  the 
  ema- 
  

   nation 
  only 
  took 
  two 
  or 
  three 
  seconds 
  to 
  condense. 
  The 
  

   rapidity 
  of 
  decay 
  of 
  activity 
  of 
  the 
  emanation 
  makes 
  the 
  

   experiment 
  extremely 
  difficult. 
  An 
  error 
  of 
  one-fifth 
  of 
  a 
  

   second 
  in 
  the 
  time 
  during 
  which 
  the 
  emanation 
  is 
  left 
  in 
  the 
  

   spiral 
  to 
  condense 
  causes 
  an 
  error 
  of 
  3*5 
  per 
  cent, 
  in 
  the 
  

   final 
  result, 
  and 
  one 
  of 
  0*5 
  second, 
  of 
  8'5 
  per 
  cent. 
  

  

  The 
  spiral 
  was 
  made 
  of 
  copper 
  tubing, 
  127 
  cm. 
  long, 
  3 
  mm. 
  

   in 
  internal 
  diameter, 
  and 
  1 
  mm. 
  thick. 
  This 
  was 
  wound 
  into 
  

   a 
  double 
  spiral 
  of 
  11 
  turns, 
  8 
  cm. 
  long, 
  the 
  mean 
  diameter 
  of 
  

   the 
  outer 
  one 
  being 
  2'5 
  cm., 
  and 
  of 
  the 
  inner 
  1*3 
  cm. 
  One 
  

   end 
  of 
  the 
  spiral 
  was 
  connected 
  by 
  means 
  of 
  a 
  rubber 
  tube, 
  

   14 
  cm. 
  long, 
  with 
  a 
  glass 
  tube 
  A 
  (fig. 
  1), 
  in 
  which 
  the 
  active 
  

   preparation 
  was 
  kept. 
  The 
  other 
  end 
  was 
  similarly 
  connected 
  

   with 
  the 
  emanation 
  electroscope, 
  a 
  stopcock 
  interposing 
  in 
  

   each 
  case, 
  so 
  that 
  both 
  the 
  tube 
  A 
  and 
  the 
  electroscope 
  could 
  

   be 
  shut 
  off 
  from 
  the 
  spiral 
  when 
  necessary. 
  The 
  copper 
  

   spiral 
  itself 
  was 
  used 
  as 
  a 
  thermometer, 
  a 
  constant 
  current 
  of 
  

   0*24 
  amp. 
  being 
  sent 
  through 
  it, 
  while 
  the 
  change 
  of 
  resist- 
  

   ance 
  was 
  measured 
  by 
  llie 
  fall 
  of 
  potential 
  between 
  two 
  

   fixed 
  points 
  on 
  the 
  spiral 
  by 
  means 
  of 
  a 
  D'Arsonval 
  galvano- 
  

   meter 
  (G). 
  The 
  current 
  was 
  adjusted 
  by 
  means 
  of 
  a 
  sliding 
  

   resistance, 
  so 
  as 
  to 
  keep 
  the 
  potential 
  difference 
  constant 
  

   between 
  two 
  other 
  points 
  in 
  the 
  circuit, 
  which 
  were 
  at 
  the 
  

   ordinary 
  temperature, 
  the 
  potential 
  difference 
  being 
  read 
  by 
  a 
  

   Weston's 
  milli-voltnieter. 
  The 
  reading 
  oi' 
  the 
  galvanometer 
  

  

  