﻿S6'^ 
  Mr. 
  F. 
  Soddy 
  on 
  the 
  

  

  The 
  initial 
  value 
  of 
  the 
  leak 
  due 
  to 
  the 
  penetrating 
  rays 
  

   was 
  75. 
  It 
  will 
  be 
  seen 
  that 
  from 
  the 
  start 
  over 
  a 
  period 
  of 
  

   33 
  dnys 
  — 
  about 
  the 
  period 
  of 
  aveiage 
  life 
  of 
  uranium 
  X, 
  in 
  

   which 
  0*632 
  of 
  the 
  total 
  disintegrates 
  — 
  the 
  a-radiation 
  has 
  

   been 
  practically 
  constant. 
  To 
  obtain 
  an 
  idea 
  of 
  the 
  growth 
  

   of 
  a-rays 
  theoretically 
  to 
  be 
  expected, 
  the 
  a-radiation 
  of 
  a 
  

   film 
  containing 
  24 
  mg. 
  of 
  uranyl 
  nitrate 
  (=12 
  mg, 
  uranium) 
  

   was 
  measured 
  in 
  hydrogen 
  under 
  precisely 
  similar 
  conditions. 
  

   It 
  gave 
  an 
  a-ray 
  leak 
  of 
  17*8. 
  The 
  growth 
  of 
  a-rays 
  to 
  be 
  

   expected 
  in 
  the 
  last 
  experiment 
  in 
  33 
  days, 
  if 
  the 
  change 
  of 
  

   uianium 
  X 
  into 
  the 
  parent 
  of 
  radium 
  occurred 
  directly, 
  is 
  

   equal 
  to 
  that 
  of 
  0'632 
  x 
  5*05 
  X 
  2 
  = 
  6*5 
  mg. 
  of 
  uranium, 
  or 
  

   about 
  9*6 
  divisions. 
  Even 
  if 
  a 
  considerable 
  reduction 
  is 
  

   made 
  for 
  the 
  fact 
  that 
  the 
  weight 
  of 
  the 
  uranium-X 
  film 
  

   was 
  about 
  three 
  times 
  the 
  weight 
  of 
  the 
  uranyl 
  nitrate 
  film, 
  

   it 
  is 
  difiicult 
  to 
  believe 
  that 
  the 
  growth 
  would 
  not 
  easily 
  

   have 
  been 
  detected 
  in 
  the 
  experiment 
  if 
  it 
  had 
  occurred. 
  

  

  In 
  the 
  preceding 
  experiment 
  with 
  the 
  preparations 
  of 
  the 
  

   third 
  separation, 
  the 
  initial 
  a-activity 
  was 
  less 
  than 
  half 
  the 
  

   value 
  in 
  the 
  last 
  experiment. 
  Any 
  rise 
  could 
  therefore 
  have 
  

   been 
  still 
  more 
  easily 
  detected. 
  But 
  up 
  to 
  the 
  period 
  of 
  

   137 
  days 
  from 
  preparation, 
  when 
  less 
  than 
  2 
  per 
  cent, 
  of 
  the 
  

   original 
  uranium 
  X 
  remains 
  undisintegrated, 
  not 
  the 
  slightest 
  

   growth 
  has 
  been 
  recorded. 
  

  

  The 
  most 
  active 
  preparation 
  of 
  the 
  second 
  separation 
  

   tested 
  recently 
  in 
  the 
  new 
  hydrogen 
  electroscope 
  in 
  hydrogen 
  

   on 
  two 
  occasions 
  200 
  days 
  and 
  227 
  days 
  from 
  preparation, 
  

   gave 
  the 
  same 
  a-ray 
  leak 
  (about 
  80). 
  The 
  best 
  preparation 
  

   of 
  the 
  first 
  separation 
  — 
  the 
  best 
  one 
  ever 
  prepared 
  from 
  the 
  

   point 
  of 
  view 
  of 
  smallness 
  of 
  mass 
  — 
  tested 
  in 
  air 
  (in 
  a 
  much 
  

   Weaker 
  field 
  than 
  now 
  used) 
  has 
  latterly, 
  now 
  that 
  the 
  

   ^-radiation 
  has 
  nearly 
  decayed, 
  shown 
  no 
  change 
  in 
  the 
  

   considerable 
  «-radiation 
  present. 
  In 
  the 
  last 
  tests 
  26^ 
  and 
  

   291 
  days 
  from 
  preparation, 
  the 
  a-leak 
  has 
  been 
  constant 
  at 
  

   35 
  (in 
  air). 
  This 
  and 
  a 
  still 
  earlier 
  preparation 
  now 
  16 
  

   months 
  old, 
  prepared 
  from 
  3 
  kilograms 
  of 
  uranyl 
  nitrate 
  in 
  

   preliminary 
  work, 
  have 
  now 
  decayed 
  so 
  far 
  that 
  their 
  

   a-radiation 
  can 
  be 
  examined 
  without 
  the 
  aid 
  of 
  a 
  magnet 
  in 
  

   an 
  ordinary 
  electroscope 
  against 
  suitable 
  standards. 
  Since 
  

   these 
  tests 
  were 
  started 
  the 
  «-radiation 
  has 
  remained 
  constant. 
  

   A 
  still 
  older 
  preparation, 
  dating 
  from 
  1903/4, 
  prepared 
  from 
  

   probably 
  not 
  more 
  than 
  50 
  grams 
  of 
  uranyl 
  nitrate, 
  has 
  also 
  

   quite 
  an 
  appreciable 
  a-radiation. 
  This 
  has 
  been 
  kept 
  under 
  

   careful 
  observation 
  for 
  over 
  a 
  year 
  and 
  no 
  change 
  has 
  been 
  

   recorded. 
  

  

  