﻿534 
  The 
  Disintegration 
  of 
  Uranium 
  X. 
  

  

  in 
  a 
  very 
  small 
  quantity 
  of 
  iron 
  was 
  dissolved 
  in 
  hydro- 
  

   fluoric 
  acid 
  and 
  placed 
  in 
  a 
  platinum 
  tray. 
  The 
  acid 
  was 
  

   slowly 
  evaporated 
  off 
  until 
  it 
  was 
  nearly 
  all 
  gone 
  when 
  the 
  

   tray 
  was 
  rapidly 
  raised 
  to 
  a 
  bright 
  red 
  heat 
  in 
  the 
  blow-pipe. 
  

   Immediately 
  it 
  was 
  cool 
  the 
  platinum 
  tray 
  was 
  taken 
  to 
  the 
  

   electroscope 
  and 
  its 
  activity 
  measured. 
  No 
  change 
  in 
  the 
  

   activity 
  of 
  the 
  material 
  in 
  the 
  tray 
  could 
  be 
  detected 
  in 
  con- 
  

   secutive 
  measurements 
  taken 
  over 
  twenty 
  minutes. 
  The 
  

   same 
  constancy 
  of 
  activity 
  was 
  seen, 
  no 
  matter 
  whether 
  

   tantalum 
  or 
  thorium 
  was 
  present 
  or 
  absent. 
  Potassium 
  bi- 
  

   fluoride 
  was 
  also 
  tried 
  in 
  place 
  of 
  hydrofluoric 
  acid, 
  but 
  no> 
  

   trace 
  of 
  any 
  disturbance 
  of 
  the 
  equilibrium 
  conditions 
  was 
  

   observed. 
  

  

  The 
  substance, 
  since 
  it 
  belongs 
  to 
  the 
  fifth 
  group, 
  should 
  

   have 
  properties 
  resembling 
  tantalum, 
  and 
  thus 
  its 
  most 
  

   definite 
  reactions 
  should 
  be 
  concerned 
  with 
  the 
  different 
  

   fluorides. 
  No 
  facts 
  of 
  importance, 
  however, 
  could 
  be 
  obtained 
  

   in 
  this 
  direction, 
  as 
  immediately 
  a 
  precipitate 
  of 
  any 
  kind 
  

   was 
  formed 
  in 
  presence 
  of 
  hydrofluoric 
  acid 
  the 
  uranium 
  X 
  1( 
  

   was 
  carried 
  along 
  with 
  it. 
  

  

  The 
  chemistry 
  of 
  uranium 
  X 
  2 
  thus 
  remains 
  extremely 
  

   vague. 
  Tantalum 
  is 
  generally 
  recognized 
  by 
  chemists 
  to 
  be 
  

   a 
  very 
  difficult 
  substance 
  to 
  work 
  with, 
  and 
  a 
  body 
  of 
  higher 
  

   atomic 
  weight 
  occupying 
  a 
  position 
  in 
  the 
  same 
  group 
  is 
  not 
  

   likely 
  to 
  have 
  more 
  distinctive 
  reactions. 
  In 
  addition 
  to 
  this,, 
  

   such 
  reactions 
  as 
  tantalum 
  possesses 
  almost 
  all 
  require 
  a 
  few 
  

   hours 
  to 
  take 
  place, 
  and 
  such, 
  of 
  course, 
  are 
  no 
  use 
  for 
  a 
  

   substance 
  of 
  which 
  the 
  period 
  of 
  average 
  life 
  is 
  1*6 
  minutes. 
  

   All 
  that 
  can 
  be 
  said 
  is 
  that 
  it 
  appears 
  to 
  resemble 
  tantalum 
  

   in 
  the 
  ease 
  with 
  which 
  it 
  is 
  precipitated, 
  but 
  it 
  has 
  not 
  been 
  

   found 
  possible 
  to 
  obtain 
  a 
  definite 
  proof 
  of 
  this 
  view. 
  

  

  It 
  is 
  of 
  interest 
  to 
  consider 
  the 
  question 
  of 
  the 
  parent 
  of 
  

   actinium. 
  Soddy 
  *", 
  in 
  his 
  paper 
  on 
  the 
  " 
  Radio-elements 
  

   and 
  the 
  Periodic 
  Law," 
  made 
  the 
  suggestion 
  that 
  if 
  the 
  still 
  

   unknown 
  substance 
  which 
  he 
  called 
  " 
  eka-tantalum 
  " 
  had 
  a 
  

   very 
  long 
  life 
  it 
  might 
  be 
  the 
  parent 
  of 
  actinium, 
  as 
  well 
  as 
  

   of 
  uranium 
  II. 
  in 
  a 
  double 
  change. 
  As 
  it 
  turns 
  out, 
  how- 
  

   ever, 
  this 
  substance 
  has 
  a 
  very 
  short 
  period, 
  and 
  consequently 
  

   it 
  cannot 
  be 
  the 
  parent 
  of 
  actinium 
  ; 
  otherwise 
  the 
  a 
  rays 
  

   necessary 
  for 
  the 
  production 
  of 
  actinium 
  would 
  be 
  easily 
  

   detectable. 
  If 
  the 
  actinium 
  series 
  is 
  connected 
  with 
  the 
  

   uranium 
  series 
  then 
  the 
  only 
  other 
  possibility 
  seems 
  to 
  be 
  

   that 
  radium 
  disintegrates 
  in 
  two 
  ways, 
  the 
  main 
  branch 
  

   being 
  formed 
  by 
  the 
  expulsion 
  of 
  an 
  a. 
  ray 
  and 
  giving 
  the 
  

   product 
  radium 
  emanation, 
  while 
  the 
  lesser 
  branch 
  is 
  formed 
  

   * 
  Soddy, 
  loc. 
  cit. 
  

  

  