﻿Determination 
  of 
  Radium 
  in 
  Radioactive 
  Substances. 
  675 
  

  

  fig. 
  1. 
  A 
  small 
  splintered 
  and 
  weighed 
  fragment 
  of 
  the 
  mineral 
  

   or 
  salt 
  (say 
  *01 
  to 
  "0001 
  gram) 
  is 
  placed 
  in 
  a 
  hollow 
  in 
  the 
  

  

  Fig-. 
  1. 
  

  

  ToS<Lope. 
  

  

  carbon 
  rod, 
  and 
  the 
  cover-glass 
  adjusted. 
  The 
  current 
  is 
  

   passed 
  through 
  the 
  rod 
  which 
  is 
  heated 
  to 
  2000° 
  0.-3000° 
  C. 
  

   for 
  from 
  10 
  to 
  30 
  seconds. 
  If 
  the 
  mineral 
  decrepitates 
  

   it 
  should 
  be 
  covered 
  with 
  a 
  fragment 
  of 
  carbon 
  to 
  prevent 
  

   its 
  escape. 
  The 
  small 
  rubber 
  balloon 
  (about 
  100 
  c.c. 
  

   capacity^ 
  allows 
  for 
  the 
  expansion 
  of 
  the 
  air 
  and 
  production 
  

   of 
  carbon 
  dioxide. 
  The 
  combined 
  effect 
  is 
  very 
  small. 
  

   The 
  electroscope, 
  which 
  had 
  been 
  exhausted, 
  refilled 
  and 
  

   observed, 
  is 
  now 
  again 
  exhausted 
  and 
  filled 
  through 
  

   the 
  chamber 
  and 
  through 
  calcium 
  chloride, 
  soda-lime, 
  

   phosphoric 
  oxide, 
  and 
  a 
  plug 
  of 
  cotton-wool 
  to 
  absorb 
  the 
  

   ions 
  generated 
  in 
  the 
  furnace. 
  These 
  tubes 
  only 
  require 
  

   refilling 
  at 
  wide 
  intervals 
  of 
  time, 
  and 
  hence 
  the 
  apparatus 
  is 
  

   always 
  ready 
  for 
  an 
  estimation, 
  which 
  may 
  be 
  made 
  in 
  from 
  

   20 
  to 
  30 
  minutes 
  in 
  all. 
  A 
  length 
  of 
  capillary 
  tubing 
  is 
  

   inserted 
  to 
  protect 
  the 
  leaf 
  and 
  ensure 
  uniformity 
  in 
  the 
  rate 
  

   of 
  filling. 
  The 
  collapse 
  of 
  the 
  leaves 
  is 
  then 
  observed 
  in 
  the 
  

   usual 
  way. 
  The 
  operation 
  does 
  not 
  involve 
  the 
  use 
  of 
  

   chemicals, 
  and 
  the 
  carbon 
  rod 
  has 
  at 
  no 
  time 
  when 
  heated 
  

   alone 
  or 
  with 
  non-radioactive 
  minerals 
  been 
  found 
  to 
  affect 
  

   the 
  discharge-rate 
  of 
  the 
  leaf 
  -system. 
  

  

  The 
  results 
  of 
  several 
  analyses 
  are 
  given 
  below 
  in 
  illustra- 
  

   tion 
  of 
  the 
  method, 
  and 
  their 
  concordance 
  is 
  a 
  sufficient 
  

   illustration 
  of 
  its 
  utility. 
  The 
  percentage 
  error 
  is 
  small 
  in 
  

   spite 
  of 
  the 
  minute 
  quantities 
  dealt 
  with. 
  As 
  the 
  mineral 
  is 
  

   not 
  powdered 
  in 
  these 
  experiments, 
  the 
  emanation 
  loss 
  in 
  the 
  

   cold 
  is 
  disregarded. 
  

  

  