﻿Relation 
  heticeen 
  Uranium 
  and 
  Radium, 
  

  

  849 
  

  

  the 
  charge 
  has 
  to 
  be 
  renewed 
  every 
  few 
  minutes. 
  At 
  first 
  

   this 
  was 
  not 
  done, 
  and 
  the 
  active 
  deposit, 
  instead 
  o£ 
  being 
  

   concentrated 
  on 
  the 
  leaf 
  system 
  in 
  the 
  most 
  favourable 
  

   position 
  to 
  produce 
  ionization, 
  is 
  distributed 
  over 
  the 
  surface 
  

   of 
  the 
  globe. 
  The 
  leak 
  under 
  these 
  circumstances 
  after 
  the 
  

   three-hour 
  interval 
  is 
  from 
  ten 
  to 
  twenty 
  per 
  cent, 
  too 
  low, 
  

   and 
  rises 
  gradually 
  with 
  successive 
  measurements 
  for 
  a 
  further 
  

   period 
  of 
  three 
  hours. 
  

  

  III. 
  Calibration 
  of 
  the 
  Electroscope, 
  

   The 
  two 
  standards 
  used 
  in 
  previous 
  work 
  had 
  been 
  made 
  

   by 
  directly 
  weighing 
  2*9 
  and 
  3"5 
  milligrams 
  of 
  pitchblende 
  

   of 
  53 
  per 
  cent, 
  uranium 
  content, 
  and 
  differed 
  from 
  each 
  

   other 
  by 
  about 
  ten 
  per 
  cent., 
  due 
  no 
  doubt 
  to 
  the 
  error 
  of 
  

   weighing 
  directly 
  such 
  small 
  quantities 
  on 
  an 
  ordinary 
  

   balance. 
  For 
  the 
  present 
  electroscope 
  an 
  entirely 
  new 
  set 
  

   of 
  six 
  standards 
  were 
  prepared 
  w^ith 
  the 
  utmost 
  care, 
  from 
  a 
  

   different 
  sample 
  of 
  pitchblende. 
  Three 
  separate 
  quantities 
  

   weighing 
  59"45, 
  133*7, 
  and 
  58*32 
  milligrams 
  were 
  separately 
  

   dissolved 
  in 
  nitric 
  acid 
  which 
  had 
  recently 
  been 
  distilled 
  

   over 
  barium 
  nitrate 
  to 
  remove 
  any 
  sulphuric 
  acid, 
  and 
  

   diluted 
  in 
  100 
  c.c. 
  graduated 
  flasks. 
  Out 
  of 
  each 
  of 
  the 
  

   three 
  solutions 
  two 
  standards 
  were 
  made, 
  by 
  taking 
  a 
  known 
  

   fraction 
  of 
  the 
  liquid, 
  determined 
  by 
  weighing, 
  and 
  sealing 
  

   it 
  up 
  after 
  dilution 
  in 
  a 
  flask 
  similar 
  to 
  A 
  (fig. 
  1) 
  of 
  about 
  

   100 
  c.c. 
  capacity. 
  These 
  six 
  new 
  standards 
  agree 
  extremely 
  

   well 
  among 
  themselves. 
  On 
  the 
  remainders 
  of 
  the 
  solutions 
  

   used 
  in 
  preparing 
  the 
  standards 
  three 
  analyses 
  of 
  uranium 
  

   were 
  performed, 
  which 
  agreed 
  in 
  showing 
  that 
  the 
  proportion 
  

   of 
  uranium 
  in 
  the 
  pitchblende 
  used 
  was 
  49 
  per 
  cent. 
  The 
  

   results 
  are 
  shown 
  in 
  Table 
  I. 
  

  

  Table 
  I. 
  

  

  Mkan 
  (omitting 
  IV.) 
  ... 
  5 
  '78 
  

  

  