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  XIV. 
  On 
  tlie 
  Distribution 
  of 
  TJioiium 
  in 
  the 
  Kartlis 
  Surface 
  

   Materials. 
  By 
  J. 
  JoLY, 
  F.E.S* 
  

  

  SUBSEQUENT 
  to 
  the 
  completion 
  o£ 
  the 
  experiments 
  

   described 
  in 
  my 
  former 
  paper 
  on 
  the 
  subject 
  of 
  the 
  

   distribution 
  of 
  thorium 
  (Phil. 
  Mag. 
  May 
  1909, 
  p. 
  760), 
  1 
  

   received 
  through 
  the 
  kindness 
  of 
  Professor 
  Sydney 
  Young 
  

   a 
  sample 
  of 
  thorianite. 
  At 
  a 
  more 
  recent 
  date 
  Professor 
  

   Wyndham 
  Dunstan 
  was 
  so 
  good 
  as 
  to 
  send 
  me 
  some 
  of 
  

   the 
  same 
  mineral 
  : 
  part 
  of 
  a 
  sample 
  which 
  he 
  himself 
  had 
  

   analysed. 
  This 
  sample 
  contains 
  79'36 
  per 
  cent, 
  of 
  thorium 
  

   oxide 
  (ThOg) 
  and 
  14*32 
  per 
  cent, 
  of 
  uranium 
  oxide 
  (UsOs). 
  

  

  A 
  standard 
  solution 
  prepared 
  from 
  the 
  first 
  mentioned 
  

   sample 
  I 
  shall 
  refer 
  to 
  as 
  solution 
  A, 
  and 
  one 
  prepared 
  from 
  

   the 
  second 
  sample, 
  solution 
  B. 
  Both 
  solutions 
  are 
  prepared 
  

   by 
  dissolving 
  one 
  decigram 
  of 
  the 
  mineral 
  in 
  a 
  few 
  cubic 
  

   centimetres 
  of 
  pure 
  nitric 
  acid 
  and 
  diluting 
  with 
  distilled 
  

   water 
  up 
  to 
  100 
  c=cs. 
  Each 
  c.c. 
  of 
  solution 
  B 
  contains, 
  

   therefore, 
  6*977x10"* 
  gram 
  of 
  elemental 
  thorium. 
  It 
  is 
  

   probable 
  that 
  solution 
  A 
  does 
  not 
  differ 
  much 
  in 
  thorium 
  

   content 
  (Dunstan, 
  Proc. 
  K. 
  S. 
  1905, 
  A, 
  p. 
  261). 
  

  

  A 
  considerable 
  number 
  of 
  experiments 
  were 
  carried 
  out 
  

   with 
  these 
  solutions; 
  and 
  the 
  constant 
  of 
  the 
  electroscope 
  was 
  

   finally 
  determined 
  by 
  means 
  of 
  solution 
  B, 
  as 
  2'2 
  x 
  10"^ 
  gram. 
  

   That 
  is 
  to 
  say, 
  a 
  gain 
  in 
  the 
  rate 
  of 
  discharge 
  of 
  one 
  scale- 
  

   division 
  per 
  hour 
  indicates 
  2*2x10"^ 
  gram 
  of 
  thorium 
  in 
  

   the 
  solution 
  being 
  dealt 
  with. 
  The 
  following 
  results 
  were 
  

   obtained 
  by 
  taking 
  in 
  each 
  case 
  one 
  c.c. 
  of 
  the 
  standard 
  

   solution 
  and 
  diluting 
  up 
  to 
  one 
  litre 
  ; 
  or, 
  again, 
  by 
  adding 
  

   the 
  standard 
  solution 
  to 
  a 
  rock 
  solution 
  : 
  — 
  

  

  Gain 
  in 
  Scale- 
  

   Divisions 
  per 
  hour. 
  

  

  Solution 
  A. 
  In 
  water 
  30 
  

  

  Same, 
  testecl 
  7 
  days 
  later 
  30 
  

  

  „ 
  In 
  water 
  strongly 
  acid 
  29 
  

  

  Same, 
  tested 
  3 
  days 
  later 
  31 
  

  

  „ 
  In 
  a 
  rock 
  solution, 
  800 
  ccs 
  29"1 
  

  

  Same, 
  tested 
  3 
  days 
  later 
  31*7 
  

  

  Same, 
  tested 
  4 
  days 
  after 
  first 
  test 
  ... 
  29 
  

   Solution 
  B. 
  In 
  water 
  32 
  

  

  Many 
  additional 
  experiments, 
  varied 
  in 
  certain 
  particulars, 
  

   agreed 
  in 
  confirming 
  the 
  approximation 
  of 
  29 
  to 
  32 
  scale- 
  

   divisions 
  per 
  hour 
  as 
  the 
  gain 
  arising 
  from 
  the 
  addition 
  of 
  

   1 
  c.c. 
  of 
  the 
  standard 
  solution 
  to 
  the 
  contents 
  of 
  the 
  boiling- 
  

   flask. 
  The 
  possibility 
  that 
  in 
  certain 
  rock 
  solutions 
  wherein 
  

   but 
  little 
  thorium 
  had 
  been 
  detected, 
  and 
  in 
  others 
  where 
  

   there 
  was 
  an 
  evident 
  want 
  of 
  limpidity, 
  some 
  cause 
  might 
  

  

  * 
  Communicated 
  by 
  the 
  Author. 
  

  

  