﻿624 
  Messrs. 
  F. 
  Soddy 
  and 
  A. 
  S. 
  Russell 
  on 
  the 
  

  

  of 
  water, 
  and 
  the 
  solutions 
  heated 
  over 
  water-baths 
  till 
  a 
  

   density 
  o£ 
  2*02 
  was 
  attained. 
  The 
  solutions 
  were 
  then 
  poured 
  

   into 
  large 
  evaporatino- 
  basins 
  and 
  allowed 
  to 
  cool 
  over 
  night. 
  

   When 
  crystallization 
  had 
  set 
  in 
  completely 
  the 
  mother-liquor 
  

   contained 
  about 
  one-third 
  of 
  the 
  total 
  weight 
  o£ 
  salt. 
  The 
  

   mother-liquors 
  from 
  each 
  set 
  of 
  crystals 
  were 
  drained 
  off", 
  

   concentrated 
  over 
  the 
  water-bath 
  to 
  the 
  same 
  density 
  as 
  

   before, 
  poured 
  out 
  and 
  allowed 
  to 
  crystallize 
  slowly. 
  The 
  

   resulting 
  mother-liquor 
  is 
  similarly 
  treated, 
  and 
  so 
  on 
  until 
  

   the 
  amount 
  of 
  uranyl 
  nitrate 
  in 
  the 
  mother-liquor 
  did 
  not 
  

   much 
  exceed 
  100 
  grams. 
  Usually 
  the 
  whole 
  of 
  the 
  crystals 
  

   so 
  obtained 
  would 
  again 
  be 
  recrystallized, 
  the 
  mother-liquor 
  

   from 
  the 
  first 
  batch 
  of 
  crystals 
  being 
  added 
  to 
  the 
  next 
  and 
  

   so 
  on, 
  while 
  the 
  end 
  fractions 
  from 
  this 
  second 
  recrystalli- 
  

   zation 
  usually 
  were 
  still 
  sufficiently 
  rich 
  in 
  uranium 
  X 
  to 
  

   be 
  worth 
  subjecting 
  to 
  a 
  third 
  recrystallization. 
  

  

  To 
  test 
  the 
  amount 
  of 
  uranium 
  X 
  remaining 
  in 
  each 
  batch 
  

   of 
  crystals 
  a 
  sample 
  of 
  about 
  40 
  grams 
  is 
  taken 
  after 
  thorough 
  

   mixing. 
  This 
  is 
  placed 
  at 
  a 
  fixed 
  distance 
  below 
  an 
  electro- 
  

   scope 
  provided 
  with 
  a 
  base 
  of 
  aluminium 
  foil 
  0*3 
  mm. 
  thick, 
  

   and 
  the 
  leak 
  it 
  produces 
  is 
  compared 
  with 
  that 
  produced 
  by 
  

   a 
  similar 
  sample 
  of 
  standard 
  uranyl 
  nitrate. 
  

  

  In 
  a 
  single 
  operation 
  arranged 
  so 
  that 
  about 
  two-t-hirds 
  of 
  

   the 
  salt 
  crystallizes 
  it 
  was 
  found 
  that 
  the 
  crystals 
  retained 
  

   from 
  15 
  to 
  30 
  per 
  cent, 
  of 
  their 
  initial 
  quantity 
  of 
  uranium 
  X, 
  

   so 
  that 
  of 
  the 
  total 
  quantity 
  of 
  the 
  latter 
  all 
  but 
  from 
  one- 
  

   sixth 
  to 
  one-ninth 
  is 
  concentrated 
  in 
  the 
  mother-liquor. 
  One- 
  

   seventh 
  may 
  be 
  taken 
  as 
  an 
  average 
  fraction. 
  In 
  n 
  similar 
  

   successive 
  crystallizations 
  the 
  quantity 
  of 
  salt 
  in 
  the 
  last 
  

   mother-liquor 
  is 
  (^)" 
  of 
  the 
  initial 
  quantity, 
  while 
  the 
  

   uranium 
  X 
  contained 
  therein 
  corresponds 
  to 
  (|-)" 
  of 
  the 
  

   initial 
  quantity. 
  Thus 
  after 
  six 
  successive 
  crystallizations 
  

   50 
  kilograms 
  would 
  yield 
  a 
  final 
  mother-liquor 
  containing 
  

   about 
  70 
  grams 
  of 
  uranyl 
  nitrate 
  together 
  with 
  the 
  uranium 
  X 
  

   from 
  20 
  kilograms 
  of 
  uranyl 
  nitrate. 
  In 
  the 
  second 
  and 
  

   third 
  series 
  of 
  recrystallizations 
  two 
  further 
  similar 
  fractions 
  

   would 
  result 
  with 
  the 
  uranium 
  X 
  respectively 
  of 
  perhaps 
  

   10 
  kilograms 
  and 
  5 
  kilograms. 
  From 
  the 
  weights 
  and 
  

   activities 
  of 
  the 
  various 
  quantities 
  of 
  crystals 
  obtained 
  as 
  the 
  

   result 
  of 
  the 
  process 
  the 
  fraction 
  of 
  the 
  total 
  uranium 
  X 
  

   separated 
  could 
  be 
  deduced. 
  In 
  the 
  second 
  separation 
  about 
  

   80 
  per 
  cent, 
  and 
  in 
  the 
  third 
  about 
  72 
  per 
  cent, 
  of 
  the 
  

   uranium 
  X 
  was 
  removed 
  by 
  crystallization. 
  

  

  The 
  next 
  step 
  in 
  the 
  operation 
  consisted 
  in 
  the 
  removal 
  of 
  

   uranium 
  from 
  the 
  concentrates 
  by 
  means 
  of 
  ammonium 
  car- 
  

   bonate. 
  Each 
  concentrate 
  as 
  it 
  was 
  obtained 
  was 
  added 
  to 
  

  

  