﻿332 
  

  

  The 
  Existence 
  of 
  Uranium 
  Y. 
  

  

  are 
  collected 
  together 
  in 
  the 
  following 
  table. 
  The 
  density 
  I> 
  

   of 
  aluminium 
  was 
  2*72. 
  

  

  

  Absorption 
  coefficient 
  fx 
  

   in 
  Aluminium. 
  

  

  Mass 
  absorption 
  coefficient 
  

   fi/~D 
  in 
  Aluminium. 
  

  

  RaB 
  

  

  T230 
  (cm.)" 
  1 
  

  

  i 
  40 
  

  

  I 
  0-51 
  „ 
  

  

  85 
  (cm.)- 
  1 
  

   14-7 
  

  

  0-188 
  „ 
  

  

  RaC 
  

  

  0115,, 
  

  

  0-0424 
  „ 
  

  

  EaD 
  

  

  r 
  45 
  „ 
  

  

  1 
  99 
  „ 
  

  

  16-5 
  

   0-36 
  „ 
  

  

  RaE 
  

  

  Nearly 
  the 
  same 
  types 
  of 
  

   radiation 
  as 
  from 
  radium 
  D, 
  

   but 
  relatively 
  very 
  feeble. 
  

  

  

  We 
  are 
  much 
  indebted 
  to 
  Dr. 
  Eussell 
  and 
  Mr. 
  Chadwick 
  

   for 
  the 
  great 
  care 
  and 
  trouble 
  they 
  have 
  taken 
  in 
  purifying 
  

   the 
  preparations 
  of 
  radium 
  D 
  and 
  radium 
  E 
  employed 
  in 
  these 
  

   experiments. 
  

  

  University 
  of 
  Manchester, 
  

   June 
  1913. 
  

  

  XX. 
  The 
  Existence 
  of 
  Uranium 
  Y. 
  

   To 
  the 
  Editors 
  of 
  the 
  Philosophical 
  Magazine. 
  

   Gentlemen, 
  — 
  

  

  IN 
  the 
  May 
  number 
  of 
  the 
  Philosophical 
  Magazine, 
  p. 
  710, 
  

   A. 
  Fleck 
  has 
  published 
  a 
  paper 
  calling 
  in 
  question 
  the 
  

   existence 
  o£ 
  uranium 
  Y, 
  a 
  branch 
  product 
  of 
  uranium 
  de- 
  

   scribed 
  by 
  me 
  in 
  a 
  previous 
  paper 
  *. 
  Be 
  is 
  unable 
  to 
  find 
  any 
  

   trace 
  of 
  the 
  existence 
  of 
  this 
  body 
  in 
  pure 
  uranium 
  com- 
  

   pounds, 
  and 
  ascribes 
  to 
  the 
  presence 
  of 
  thorium 
  products 
  the 
  

   abnormal 
  results 
  obtained 
  by 
  me 
  for 
  the 
  initial 
  decay 
  of 
  the 
  

   soft 
  /3 
  rays 
  of 
  uranium 
  X 
  which 
  I 
  attributed 
  to 
  the 
  existence 
  

   of 
  a 
  new 
  product 
  uranium 
  Y. 
  

  

  Even 
  if 
  my 
  preparations 
  were 
  not 
  wholly 
  free 
  from 
  traces 
  of 
  

   thorium 
  and 
  its 
  products, 
  it 
  is 
  nevertheless 
  extremely 
  difficult 
  

   to 
  understand 
  how 
  the 
  presence 
  of 
  such 
  thorium 
  products 
  as 
  

   would 
  be 
  separated 
  with 
  the 
  uranium 
  X 
  in 
  the 
  methods 
  

   employed 
  by 
  me 
  would 
  simulate 
  the 
  appearance 
  of 
  a 
  single 
  

   body 
  expelling 
  soft 
  ft 
  rays 
  and 
  decaying 
  from 
  the 
  time 
  of 
  

   separation 
  with 
  a 
  period 
  of 
  about 
  1*5 
  days. 
  Moreover, 
  it 
  

  

  * 
  Phil. 
  Mag. 
  vol. 
  xxii. 
  p. 
  431 
  (1911). 
  

  

  