﻿938 
  Prof. 
  Rutherford 
  and 
  Mr. 
  Richardson 
  : 
  Analysis 
  of 
  

  

  To 
  overcome 
  this 
  difficulty, 
  the 
  various 
  active 
  products 
  were 
  

   separated 
  from 
  a 
  preparation 
  of 
  mesothorium, 
  which 
  had 
  a 
  

   Y-ray 
  activity 
  equal 
  to 
  about 
  2*5 
  milligrams 
  of 
  radium. 
  

   Since 
  mesothorium 
  always 
  contains 
  some 
  radium, 
  which 
  

   is 
  inseparable 
  from 
  it, 
  it 
  was 
  necessary 
  to 
  take 
  precautions 
  

   that 
  none 
  of 
  the 
  Y-ray 
  products 
  of 
  the 
  latter 
  should 
  interfere 
  

   in 
  the 
  measurements. 
  

  

  The 
  mesothorium 
  was 
  dissolved 
  in 
  a 
  very 
  small 
  quantity 
  of 
  

   dilute 
  HC1 
  and 
  the 
  solution 
  made 
  up 
  to 
  0'5 
  c.c. 
  This 
  

   solution 
  was 
  heated 
  on 
  a 
  water-bath 
  for 
  six 
  hours, 
  in 
  order 
  

   to 
  drive 
  off 
  any 
  radium 
  emanation 
  formed 
  in 
  the 
  interval. 
  

   During 
  that 
  time 
  any 
  radium 
  B 
  or 
  radium 
  C 
  present 
  prac- 
  

   tically 
  disappeared. 
  A 
  nickel 
  wire 
  *3 
  mm. 
  in 
  diameter 
  was 
  

   then 
  rotated 
  in 
  the 
  solution 
  for 
  about 
  30 
  minutes, 
  in 
  order 
  

   to 
  collect 
  the 
  thorium 
  C 
  upon 
  it. 
  The 
  nickel 
  wire 
  was 
  

   found 
  to 
  be 
  sufficiently 
  active 
  to 
  show 
  a 
  strong 
  Y-ray 
  activity 
  

   in 
  the 
  electroscope, 
  and 
  the 
  purity 
  of 
  the 
  deposit 
  of 
  thorium 
  C 
  

   was 
  confirmed 
  by 
  examining 
  its 
  rate 
  of 
  decay. 
  The 
  Y" 
  ra 
  y 
  

   effect 
  due 
  to 
  the 
  nickel 
  wire 
  in 
  this 
  case 
  arose 
  not 
  from 
  

   the 
  thorium 
  C, 
  which 
  is 
  an 
  a-ray 
  product, 
  but 
  from 
  the 
  

   thorium 
  D. 
  

  

  By 
  suitable 
  chemical 
  operations 
  the 
  mesothorium 
  was 
  

   separated 
  from 
  the 
  radiothorium. 
  A 
  few 
  details 
  of 
  the 
  

   chemical 
  methods 
  employed 
  will 
  be 
  given, 
  and 
  we 
  desire 
  

   to 
  express 
  our 
  thanks 
  to 
  Dr. 
  Russell 
  and 
  Mr. 
  Chad 
  wick 
  

   for 
  kindly 
  undertaking 
  the 
  work 
  of 
  chemical 
  separation. 
  

  

  To 
  the 
  acid 
  solution 
  of 
  mesothorium 
  a 
  few 
  milligrams 
  of 
  

   aluminium 
  chloride 
  were 
  added. 
  Pure 
  ammonia 
  gas 
  was 
  

   then 
  passed 
  into 
  this 
  solution 
  and 
  aluminium 
  hydroxide 
  was 
  

   precipitated. 
  With 
  this 
  came 
  down 
  also 
  the 
  products 
  meso- 
  

   thorium 
  2, 
  radiothorium, 
  thorium 
  B, 
  thorium 
  C, 
  thorium 
  D, 
  

   and 
  any 
  trace 
  of 
  radium 
  B 
  and 
  radium 
  that 
  might 
  be 
  

   present. 
  This 
  precipitate 
  was 
  filtered 
  off 
  and 
  re-dissolved 
  

   in 
  a 
  small 
  quantity 
  of 
  dilute 
  hydrochloric 
  acid. 
  10 
  milli- 
  

   grams 
  of 
  lead 
  chloride 
  were 
  then 
  added, 
  and 
  H 
  2 
  S 
  was 
  

   passed 
  through 
  the 
  solution. 
  The 
  precipitate 
  of 
  lead 
  

   sulphide 
  was 
  filtered 
  off 
  and 
  carried 
  with 
  it 
  the 
  radium 
  B, 
  

   radium 
  C, 
  thorium 
  B, 
  thorium 
  C, 
  and 
  thorium 
  D. 
  If 
  any 
  

   radium 
  B 
  or 
  radium 
  were 
  present, 
  these 
  would 
  decay 
  in 
  

   the 
  course 
  of 
  a 
  few 
  hours, 
  and 
  the 
  source 
  then 
  consisted 
  

   of 
  thorium 
  (B 
  + 
  C 
  + 
  D) 
  in 
  equilibrium. 
  Since 
  the 
  radiation 
  

   from 
  thorium 
  (C 
  + 
  D) 
  was 
  determined 
  in 
  the 
  case 
  of 
  the 
  

   deposit 
  on 
  the 
  nickel 
  wire, 
  the 
  y 
  radiation 
  from 
  thorium 
  B 
  

   could 
  be 
  deduced 
  by 
  a 
  comparison 
  of 
  the 
  absorption 
  curves 
  

   in 
  the 
  two 
  cases. 
  

  

  The 
  filtrate 
  was 
  evaporated 
  to 
  dryness 
  and 
  the 
  H 
  2 
  S 
  

  

  