﻿the 
  Actii 
  

  

  and 
  Thorium 
  Emanations. 
  

  

  125 
  

  

  the 
  inner 
  surface 
  of 
  the 
  electroscope, 
  but 
  the 
  correction 
  due 
  

   to 
  this 
  cause 
  could 
  be 
  easily 
  made 
  by 
  measuring 
  the 
  activity 
  

   after 
  50 
  or 
  60 
  seconds, 
  when 
  all 
  the 
  emanation 
  had 
  practically 
  

   died 
  away. 
  At 
  the 
  same 
  time 
  the 
  galvanometer 
  reading 
  was 
  

   taken 
  to 
  obtain 
  the 
  temperature 
  of 
  the 
  spiral. 
  The 
  position 
  

   of 
  the 
  zero 
  point 
  of 
  the 
  galvanometer 
  was 
  verified 
  between 
  

   each 
  pair 
  of 
  readings. 
  The 
  process 
  was 
  repeated 
  about 
  every 
  

   5 
  degrees. 
  It 
  was 
  found 
  that 
  the 
  actinium 
  emanation 
  began 
  

   to 
  condense 
  at 
  about 
  —120° 
  C, 
  and, 
  just 
  as 
  in 
  the 
  case 
  of 
  

   the 
  thorium 
  emanation, 
  some 
  remained 
  uncondensed 
  below 
  

   that 
  temperature, 
  The 
  behaviour 
  was 
  the 
  same 
  whether 
  the 
  

   emanation 
  was 
  conveyed 
  by 
  air 
  or 
  by 
  hydrogen 
  within 
  the 
  

   limits 
  of 
  error 
  of 
  observation, 
  but 
  it 
  varied 
  largely 
  according 
  

   to 
  the 
  pressure 
  at 
  which 
  the 
  condensation 
  took 
  place. 
  

  

  To 
  test 
  the 
  nature 
  of 
  this 
  variation, 
  glass 
  tubes 
  varying 
  in 
  

   volume 
  were 
  inserted 
  between 
  A 
  and 
  the 
  stopcock 
  C. 
  The 
  

   results 
  are 
  shown 
  in 
  fig. 
  2, 
  in 
  which 
  the 
  abscissa 
  represents 
  

  

  Fig. 
  2. 
  (Actinium 
  Emanation). 
  

  

  

  ^20 
  

  

  <o 
  

  

  o 
  

   2 
  16 
  

  

  CO 
  

  

  g 
  14 
  

  

  

  H 
  

  

  § 
  2 
  

  

  o 
  

  

  3 
  n 
  

  

  U 
  y^ 
  5" 
  ^- 
  -*— 
  ° 
  -* 
  

  

  / 
  / 
  * 
  

  

  / 
  / 
  ^-*- 
  ° 
  a 
  *3 
  

  

  If 
  y^ 
  

  

  

  I 
  / 
  /" 
  ^-- 
  -*~~" 
  * 
  ' 
  

  

  

  ' 
  uh 
  T 
  

  

  iJM-t 
  

  

  77M 
  A 
  

  

  Mr 
  

  

  ^ 
  -160 
  -155 
  -150 
  -145 
  -140 
  -135 
  -130 
  -125 
  -120 
  -115 
  -110 
  "105 
  -100 
  -95 
  

  

  Temperature. 
  

  

  the 
  temperature, 
  and 
  the 
  ordinate 
  s 
  T 
  — 
  s 
  , 
  which 
  is 
  proportional 
  

   to 
  the 
  amount 
  of 
  emanation 
  escaping 
  uncondensed. 
  Curve 
  (1) 
  

   is 
  the 
  experiment 
  without 
  any 
  glass 
  tube, 
  (2) 
  with 
  a 
  glass 
  

   tube 
  about 
  2*5 
  mm. 
  in 
  diameter 
  and 
  6 
  cm. 
  long, 
  (3) 
  with 
  one 
  

   of 
  18 
  cm., 
  (4) 
  with 
  one 
  of 
  24 
  cm., 
  and 
  (5) 
  at 
  atmospheric 
  

   pressure. 
  The 
  scale 
  of 
  (5) 
  is 
  slightly 
  reduced 
  in 
  the 
  diagram. 
  

   Each 
  curve 
  is 
  obtained 
  from 
  two 
  or 
  three 
  experiments 
  under 
  

  

  %%taz 
  

  

  