﻿Disintegration 
  of 
  Uranium 
  A. 
  533 
  

  

  through 
  0*0034 
  mm. 
  thick 
  aluminium 
  foil. 
  This 
  curve 
  does 
  

   not 
  at 
  all 
  coincide 
  with 
  the 
  theoretical 
  curve, 
  and 
  would 
  not, 
  

   if 
  extrapolated 
  backwards, 
  cut 
  the 
  axis 
  at 
  the 
  moment 
  of 
  

   precipitation 
  near 
  zero. 
  This 
  therefore 
  shows 
  that 
  uranium 
  X 
  : 
  

   gives 
  non-penetrating 
  radiations, 
  and, 
  as 
  it 
  is 
  known 
  to 
  give 
  

   off 
  no 
  z. 
  rays, 
  these 
  rajs 
  must 
  be 
  the 
  soft 
  (ft) 
  rays. 
  Fajans 
  

   and 
  Gohring's 
  conclusion 
  that 
  the 
  hard 
  ft 
  rays 
  of 
  uranium 
  X 
  

   come 
  from 
  uranium 
  X 
  2 
  has 
  therefore 
  been 
  confirmed. 
  

  

  When 
  barium 
  sulphate 
  or 
  thorium 
  oxalate 
  is 
  precipitated 
  

   in 
  a 
  uranium 
  X 
  solution, 
  uranium 
  X 
  2 
  seems 
  to 
  remain 
  in 
  

   solution 
  in 
  excess 
  over 
  uranium 
  X^ 
  but, 
  owing 
  to 
  the 
  diffi- 
  

   culties 
  of 
  filtering, 
  four 
  to 
  five 
  minutes 
  elapse 
  between 
  the 
  

   instant 
  of 
  precipitation 
  and 
  the 
  first 
  measurement 
  in 
  the 
  

   electroscope. 
  After 
  this 
  lapse 
  of 
  time 
  very 
  little 
  change 
  

   can 
  be 
  expected 
  in 
  the 
  activity 
  of 
  the 
  precipitate, 
  so 
  that 
  it 
  

   is 
  not 
  possible 
  to 
  say 
  definitely 
  whether 
  the 
  curve 
  extra- 
  

   polated 
  backwards 
  would 
  cut 
  the 
  axis 
  near 
  zero. 
  

  

  The 
  substance 
  is 
  somewhat 
  similar 
  to 
  bismuth 
  in 
  respect 
  

   that 
  it 
  is 
  soluble 
  in 
  acid 
  solutions, 
  but 
  tends 
  to 
  be 
  precipitated 
  

   on 
  addition 
  of 
  water. 
  Tt 
  is, 
  however, 
  distinct 
  from 
  that 
  

   element 
  in 
  respect 
  of 
  solubility 
  and 
  of 
  volatility. 
  In 
  the 
  

   experiment 
  described 
  above, 
  in 
  which 
  a 
  complete 
  separation 
  

   of 
  uranium 
  X 
  2 
  was 
  obtained, 
  on 
  allowing 
  the 
  filtrate 
  to 
  stand 
  

   a 
  further 
  precipitate 
  of 
  bismuth 
  oxvchloride 
  came 
  down, 
  

   showing 
  that 
  although 
  the 
  whole 
  of 
  the 
  uranium 
  X 
  2 
  had 
  

   been 
  precipitated, 
  only 
  a 
  fraction 
  of 
  the 
  bismuth 
  had 
  been 
  

   removed. 
  Uranium 
  X 
  2 
  is 
  therefore, 
  under 
  these 
  conditions, 
  

   less 
  soluble 
  than 
  bismuth. 
  A 
  preparation 
  of 
  uranium 
  X 
  

   containing 
  iron 
  and 
  bismuth 
  was 
  ground 
  to 
  a 
  powder 
  with 
  a 
  

   quantity 
  of 
  iodine. 
  The 
  powder 
  was 
  then 
  placed 
  in 
  a 
  tray 
  

   and 
  heated 
  quickly 
  to 
  a 
  bright 
  red 
  heat 
  in 
  the 
  blow-pipe. 
  

   A 
  relatively 
  cool 
  piece 
  of 
  copper 
  foil 
  held 
  above 
  the 
  tray 
  

   collected 
  volatilized 
  bismuth 
  iodide 
  in 
  appreciable 
  quantities, 
  

   but 
  it 
  was 
  quite 
  inactive. 
  On 
  measuring 
  the 
  activity 
  of 
  the 
  

   tray 
  immediately 
  it 
  became 
  cool 
  no 
  disturbance 
  of 
  the 
  equi- 
  

   librium 
  activity 
  was 
  observed. 
  Uranium 
  X 
  2 
  is 
  thus 
  shown 
  

   to 
  be 
  less 
  volatile 
  than 
  bismuth. 
  

  

  From 
  the 
  theoretical 
  considerations 
  referred 
  to, 
  uranium 
  X 
  

   should 
  belong 
  to 
  the 
  tantalum 
  group 
  of 
  metals, 
  and 
  there- 
  

   fore 
  Soddy 
  proposed 
  to 
  call 
  the 
  substance 
  '* 
  eka-tantalum." 
  

   Tantalum 
  itself 
  is 
  not 
  a 
  volatile 
  substance, 
  but 
  the 
  fluoride 
  

   of 
  tantalum 
  is 
  appreciably 
  volatile, 
  more 
  so 
  than 
  that 
  of 
  

   niobium. 
  So 
  that 
  since 
  uranium 
  X 
  2 
  has 
  a 
  higher 
  atomic 
  

   weight 
  than 
  tantalum 
  one 
  would 
  expect 
  that 
  the 
  fluoride 
  

   should 
  also 
  be 
  volatile. 
  Under 
  no 
  circumstances, 
  however, 
  

   could 
  the 
  substance 
  be 
  volatilized. 
  Uranium 
  X 
  contained 
  

  

  