﻿C 
  674 
  ] 
  

  

  LIV. 
  A 
  Method 
  for 
  tlie 
  Determination 
  of 
  Radium 
  in 
  Radio- 
  

   active 
  Substances. 
  By 
  Arnold 
  Lockhart 
  Fletcher, 
  

   M.A,, 
  23. 
  E., 
  Royal 
  College 
  of 
  Science 
  for 
  Ireland*. 
  

  

  fl^HE 
  radium 
  content 
  of 
  certain 
  radioactive 
  substances 
  

   JL 
  has 
  been 
  given 
  by 
  Professor 
  Strutt 
  in 
  a 
  paper 
  on 
  

   the 
  uranium-radium 
  ratio 
  of 
  minerals 
  by 
  the 
  method 
  of 
  

   heating 
  the 
  powdered 
  mineral 
  in 
  a 
  glass 
  tube 
  and 
  trans- 
  

   ferring 
  the 
  liberated 
  emanation 
  to 
  an 
  electroscope 
  f 
  . 
  It 
  has 
  

   been 
  pointed 
  out 
  by 
  Boltwood 
  % 
  that 
  in 
  certain 
  cases 
  the 
  

   incomplete 
  de-emanation 
  of 
  the 
  powder 
  may 
  involve 
  an 
  error 
  

   which 
  may 
  amount 
  to 
  as 
  much 
  as 
  46 
  per 
  cent, 
  in 
  a 
  mineral 
  

   heated 
  to 
  redness. 
  

  

  The 
  method 
  described 
  in 
  the 
  present 
  paper, 
  which 
  is 
  essen- 
  

   tially 
  that 
  first 
  employed 
  by 
  Professor 
  Strutt, 
  was 
  devised 
  in 
  

   order 
  to 
  minimise 
  the 
  possibility 
  of 
  the 
  source 
  of 
  error 
  men- 
  

   tioned, 
  is 
  at 
  the 
  same 
  time 
  very 
  simply 
  carried 
  out 
  and 
  does 
  

   not 
  involve 
  the 
  use 
  of 
  any 
  apparatus 
  outside 
  the 
  scope 
  of 
  the 
  

   laboratory. 
  The 
  analyses 
  are 
  carried 
  out 
  more 
  rapidly 
  than 
  

   is 
  the 
  case 
  with 
  the 
  electric 
  furnace, 
  with 
  accuracy 
  and 
  

   without 
  expense. 
  

  

  The 
  micro-furnace, 
  an 
  instrument 
  for 
  rapid 
  analysis 
  of 
  

   alloys 
  and 
  minerals 
  which 
  has 
  been 
  elsewhere 
  described 
  more 
  

   fully 
  by 
  me, 
  is 
  used. 
  It 
  consists 
  of 
  a 
  brass 
  drum 
  sliding 
  on 
  

   a 
  slate 
  cylinder 
  which 
  is 
  perforated 
  from 
  below 
  to 
  allow 
  of 
  

   the 
  passage 
  of 
  two 
  wires 
  connected 
  to 
  terminals 
  on 
  the 
  upper 
  

   face 
  of 
  the 
  cylinder. 
  These 
  terminals 
  clamp 
  a 
  thin 
  rod 
  of 
  

   arc 
  carbon 
  which 
  is 
  heated 
  by 
  the 
  passage 
  of 
  an 
  electric 
  

   current 
  of 
  about 
  10 
  amperes 
  per 
  sq. 
  mm. 
  of 
  cross-section 
  

   (max.). 
  The 
  brass 
  drum, 
  which 
  slides 
  on 
  the 
  cylinder, 
  may 
  

   be 
  adjusted 
  in 
  any 
  position, 
  and 
  the 
  size 
  of 
  the 
  chamber 
  

   varied 
  accordingly. 
  This 
  chamber 
  is 
  enclosed 
  above 
  by 
  a 
  

   plate 
  of 
  glass 
  or 
  transparent 
  silica 
  cemented 
  to 
  a 
  brass 
  frame 
  

   resting 
  on 
  the 
  rim 
  of 
  the 
  drum. 
  In 
  these 
  experiments 
  the 
  

   upper 
  rim 
  was 
  greased 
  with 
  vaseline, 
  and 
  the 
  lower 
  rim 
  

   covered 
  by 
  a 
  rubber 
  band 
  to 
  prevent 
  leakage. 
  In 
  this 
  appli- 
  

   cation 
  of 
  the 
  micro-furnace 
  a 
  chamber 
  of 
  adjustable 
  size 
  is 
  

   not 
  necessary, 
  and 
  the 
  estimation 
  may 
  be 
  carried 
  out 
  in 
  any 
  

   box 
  fitted 
  with 
  inlet 
  and 
  outlet 
  tubes 
  and 
  terminal 
  clamps 
  to 
  

   make 
  contact 
  with 
  a 
  carbon 
  rod. 
  

  

  The 
  general 
  disposition 
  of 
  the 
  apparatus 
  is 
  shown 
  in 
  

  

  * 
  Communicated 
  by 
  the 
  Author. 
  

  

  t 
  Strutt, 
  Proc. 
  Roy. 
  Soc. 
  lxxiii. 
  p. 
  191 
  (1904). 
  

  

  X 
  Boltwood, 
  Am. 
  Jour. 
  Sci. 
  xxy. 
  p. 
  294 
  (1908). 
  

  

  