﻿676 
  

  

  Mr. 
  A. 
  L. 
  Fletcher 
  on 
  a 
  Method 
  for 
  the 
  

  

  The 
  following 
  table 
  shows 
  the 
  comparison 
  between 
  the 
  

   ratio 
  of 
  the 
  weights 
  of 
  some 
  minerals 
  tested 
  and 
  the 
  ratio 
  of 
  

   the 
  corresponding 
  gains 
  in 
  leak 
  conferred 
  upon 
  the 
  electro- 
  

   scope. 
  The 
  absolute 
  results 
  are 
  in 
  all 
  cases 
  approximately 
  

   those 
  which 
  are 
  to 
  be 
  expected 
  from 
  the 
  uranium 
  content 
  of 
  

   the 
  mineral. 
  The 
  number 
  obtained 
  for 
  the 
  constant 
  of 
  

   electroscope 
  A 
  (0*7 
  x 
  10~ 
  12 
  ) 
  is 
  identical 
  with 
  that 
  obtained 
  

   for 
  a 
  similar 
  electroscope 
  in 
  many 
  experiments 
  by 
  the 
  solu- 
  

   tion 
  and 
  tube-furnace 
  methods. 
  

  

  Mineral. 
  

  

  Amount 
  

  

  taken 
  in 
  

  

  grauis. 
  

  

  Gain 
  in 
  rate 
  

   of 
  electroscope 
  

   leak 
  3 
  hrs. 
  after 
  

  

  admission 
  in 
  

   scale-divs. 
  p. 
  h. 
  

  

  Ratio 
  

  

  of 
  wts. 
  

   taken. 
  

  

  Ratio 
  

   of 
  

  

  leaks. 
  

  

  10 
  

  

  0-8 
  

   20 
  

  

  Constant 
  Radiu 
  ™ 
  

   ofelec- 
  Present 
  

  

  troscopes 
  . 
  

  

  vIO 
  12 
  . 
  

  

  A 
  xu 
  per 
  gram. 
  

  

  Uraninite 
  Jo'" 
  

  

  (Elec 
  A) 
  |jj 
  ;;; 
  

  

  •0003 
  

  

  •000205 
  

  

  •0006 
  

  

  87 
  

  

  70 
  

  

  175 
  

  

  1-0 
  

   07 
  

  

  20 
  

  

  0-7 
  

   06 
  

  

  0-7 
  

  

  

  fl 
  ... 
  

  

  Uraninite 
  12... 
  

   (Elec. 
  B) 
  1 
  3 
  ... 
  

  

  u 
  ... 
  

  

  •0004 
  

   •0006 
  

   •0009 
  

   •0007 
  

  

  64 
  

  

  95 
  

  

  145 
  

  

  110 
  

  

  114 
  

   150 
  

  

  185 
  

  

  10 
  

   1-5 
  

   2-2 
  

   1-7 
  

  

  1-0 
  

  

  1-5 
  

   2-3 
  

   1-7 
  

  

  1-28 
  

   1-27 
  

   1-36 
  

   1-30 
  

  

  1-99 
  

   1-71 
  

   1-57 
  

  

  fl 
  ... 
  

  

  Gummite 
  . 
  \ 
  2 
  . 
  . 
  . 
  

  

  1-3 
  ... 
  

  

  •0004 
  

  

  •000625 
  

  

  •0008 
  

  

  1-0 
  

   1-6 
  

  

  2-0 
  

  

  10 
  

  

  1-3 
  

   1-6 
  

  

  1-0 
  

   1-3 
  

  

  

  Torbernite. 
  1 
  " 
  

  

  •00025 
  

   •00028 
  

  

  35 
  

   44 
  

  

  10 
  

   1-1 
  

  

  1-10 
  

  

  ... 
  1 
  0-98 
  

  

  Euxenite 
  . 
  j 
  9 
  

  

  •00041 
  

   •0022 
  

  

  21 
  

   133 
  

  

  10 
  

  

  54 
  

  

  1-0 
  

   63 
  

  

  

  0-36 
  

   0-43 
  

  

  Escape 
  of 
  Emanation 
  in 
  relation 
  to 
  Temperature. 
  

  

  The 
  following 
  curve 
  was 
  obtained 
  by 
  means 
  of 
  a 
  thermo- 
  

   couple 
  placed 
  between 
  two 
  square 
  carbon 
  rods 
  placed 
  side 
  by 
  

   side 
  and 
  heated, 
  and 
  shows 
  the 
  relation 
  between 
  the 
  amount 
  

   of 
  emanation 
  liberated 
  from 
  a 
  small 
  quantity 
  of 
  uraninite 
  in 
  

   one 
  minute 
  and 
  the 
  temperature 
  at 
  which 
  the 
  uraninite 
  is 
  

   maintained. 
  The 
  mineral 
  speck 
  was 
  kept 
  at 
  the 
  particular 
  

   temperature 
  for 
  one 
  minute, 
  and 
  the 
  disengaged 
  emanation 
  

   drawn 
  off. 
  The 
  total 
  heating 
  extended 
  for 
  2 
  minutes. 
  

  

  The 
  curve 
  obtained 
  shows 
  that 
  the 
  emanation 
  does 
  not 
  begin 
  

   to 
  come 
  off 
  freely 
  under 
  750° 
  C 
  , 
  near 
  which 
  temperature 
  

   the 
  sharp 
  bend 
  shows 
  a 
  rapid 
  increase 
  in 
  the 
  amount 
  

   liberated. 
  The 
  points 
  obtained 
  can 
  be 
  repeated 
  to 
  within 
  

   one 
  or 
  two 
  per 
  cent. 
  The 
  observations 
  made 
  by 
  Boltwood 
  * 
  

  

  * 
  Am. 
  Jour. 
  Sci. 
  xviii. 
  p. 
  97, 
  footnote 
  (1904). 
  

  

  