﻿'602 
  Prof. 
  E. 
  Rutherford 
  : 
  Experiments 
  

  

  was 
  pumped 
  off 
  together 
  with 
  a 
  large 
  quantity 
  of 
  hydrogen 
  

   and 
  oxygen 
  formed 
  in 
  solution. 
  After 
  the 
  method 
  employed 
  

   by 
  Ramsay 
  and 
  Cameron, 
  this 
  was 
  sparked 
  down 
  and 
  a 
  small 
  

   quantity 
  of 
  oxygen 
  added 
  in 
  order 
  to 
  reduce 
  the 
  excess 
  of 
  

   hydrogen. 
  The 
  emanation, 
  mixed 
  with 
  about 
  1 
  cc. 
  of 
  

   hydrogen, 
  was 
  then 
  collected 
  over 
  mercury 
  in 
  a 
  small 
  burette 
  

   in 
  which 
  was 
  placed 
  a 
  piece 
  of 
  caustic 
  potash 
  in 
  order 
  to 
  

   absorb 
  any 
  carbon 
  dioxide 
  present. 
  The 
  apparatus 
  for 
  puri- 
  

   fication 
  of 
  the 
  emanation 
  and 
  measurement 
  of 
  its 
  volume 
  is 
  

   shown 
  in 
  fig. 
  1. 
  The 
  measuring 
  apparatus 
  consisted 
  essen- 
  

   tially 
  of 
  a 
  Macleod 
  gauge. 
  A 
  capillary 
  tube, 
  15 
  cms. 
  long 
  

   and 
  0*58 
  mm. 
  diameter, 
  was 
  attached 
  to 
  a 
  long 
  glass 
  tube 
  of 
  

   volume 
  about 
  25 
  cubic 
  cms. 
  By 
  raising 
  the 
  reservoir 
  with 
  

   the 
  stopcock 
  A 
  closed, 
  the 
  gas 
  in 
  the 
  tube 
  E 
  was 
  forced 
  into 
  

   the 
  capillary 
  tube 
  F 
  and 
  its 
  volume 
  measured. 
  A 
  mercury 
  

   trap 
  R 
  was 
  used 
  to 
  avoid 
  the 
  entrance 
  of 
  any 
  gas 
  which 
  crept 
  

   along 
  the 
  surface 
  of 
  the 
  glass. 
  The 
  general 
  method 
  of 
  

   purification 
  of 
  the 
  emanation 
  is 
  best 
  seen 
  from 
  a 
  description 
  

   of 
  an 
  experiment*. 
  

  

  The 
  whole 
  apparatus 
  was 
  first 
  exhausted 
  to 
  a 
  low 
  vacuum 
  

   by 
  means 
  of 
  a 
  mercury 
  pump. 
  The 
  emanation, 
  conveyed 
  

   with 
  about 
  1 
  cc. 
  of 
  gas, 
  was 
  transferred 
  over 
  mercury 
  into 
  

   the 
  reservoir 
  C. 
  The 
  stopcocks 
  A 
  and 
  B 
  were 
  closed, 
  and 
  

   the 
  emanation 
  was 
  forced 
  by 
  raising 
  the 
  mercury 
  reservoir 
  

   through 
  the 
  stopcock 
  H 
  along 
  the 
  tube 
  D, 
  coated 
  with 
  caustic 
  

   potash, 
  into 
  the 
  U-tube 
  T. 
  The 
  U-tube, 
  of 
  volume 
  about 
  

   1*5 
  c.cms., 
  was 
  surrounded 
  by 
  liquid 
  air 
  in 
  order 
  to 
  condense 
  

   the 
  emanation. 
  The 
  whole 
  emanation 
  was 
  condensed 
  by 
  

   successively 
  raising 
  and 
  lowering 
  the 
  mercury 
  in 
  the 
  reser- 
  

   voir. 
  The 
  stopcock 
  B 
  was 
  then 
  opened 
  into 
  the 
  pump 
  and 
  

   the 
  uncondensed 
  gases 
  completely 
  pumped 
  off. 
  The 
  mercury 
  

   was 
  then 
  lowered 
  in 
  the 
  tube 
  D 
  to 
  the 
  position 
  of 
  the 
  dotted 
  

   line 
  in 
  the 
  figure. 
  The 
  liquid 
  air 
  was 
  then 
  removed. 
  The 
  

   emanation 
  after 
  volatilization 
  was 
  left 
  some 
  hours 
  in 
  contact 
  

   with 
  the 
  caustic 
  potash 
  in 
  the 
  tube 
  D 
  to 
  remove 
  the 
  last 
  trace 
  

   of 
  carbon 
  dioxide. 
  The 
  U-tube 
  was 
  then 
  surrounded 
  by 
  a 
  

   vessel 
  filled 
  with 
  pentane, 
  which 
  was 
  cooled 
  down 
  by 
  liquid 
  

   air 
  to 
  a 
  temperature 
  between 
  the 
  temperature 
  of 
  condensation 
  

   of 
  the 
  emanation 
  ( 
  — 
  150° 
  C.) 
  and 
  the 
  temperature 
  of 
  liquid 
  

   air 
  (—186° 
  C). 
  The 
  whole 
  apparatus 
  was 
  then 
  completely 
  

   exhausted 
  again 
  by 
  the 
  mercury 
  pump, 
  a 
  portion 
  of 
  the 
  

   emanation 
  being 
  volatilized 
  during 
  the 
  process 
  and 
  removed 
  

   by 
  the 
  pump. 
  Finally, 
  when 
  a 
  very 
  low 
  vacuum 
  was 
  

  

  * 
  In 
  this 
  work, 
  I 
  have 
  found 
  the 
  methods 
  developed 
  by 
  Ramsay 
  and 
  

   others 
  for 
  manipulating 
  small 
  quantities 
  of 
  gases 
  of 
  great 
  assistance. 
  See 
  

   Travers, 
  " 
  Studv 
  of 
  Gases." 
  

  

  