﻿24- 
  Penfield 
  and 
  Warren 
  — 
  Composition 
  of 
  Par 
  isite. 
  

   The 
  ratios 
  derived 
  from 
  the 
  foregoing 
  analyses 
  are 
  as 
  follows 
  : 
  

  

  CO2 
  : 
  F 
  : 
  (Ce; 
  La, 
  Di).203 
  : 
  CaO 
  

  

  I 
  -521 
  : 
  -310 
  : 
  'lee 
  : 
  '196 
  = 
  3-00 
  : 
  1-79 
  : 
  0*96 
  : 
  1-13 
  

  

  II. 
  -550 
  : 
  -359 
  : 
  -183 
  : 
  -191 
  — 
  3*00 
  : 
  1-96 
  : 
  I'Ol 
  : 
  1-04 
  

  

  III. 
  -533 
  : 
  -292 
  : 
  '187 
  : 
  'ISO 
  = 
  3*00 
  : 
  1'65 
  : 
  1-05 
  : 
  1-01 
  

  

  The 
  new 
  analysis 
  of 
  the 
  exceptionally 
  pure 
  material 
  from 
  

   Muso 
  Yalley 
  gives 
  a 
  ratio 
  approximating 
  very 
  close 
  to 
  3:2:1:1. 
  

   The 
  material 
  from 
  Montana 
  is 
  not 
  so 
  pure, 
  consequently 
  the 
  

   ratio 
  is 
  less 
  satisfactory. 
  The 
  fluorine 
  in 
  the 
  mineral 
  doubtless 
  

   caused 
  some 
  of 
  the 
  gangue 
  material 
  to 
  go 
  into 
  solution, 
  thus 
  

   causing 
  the 
  calcium 
  to 
  be 
  a 
  little 
  high 
  ; 
  while 
  the 
  fluorine 
  is 
  

   evidently 
  low, 
  because, 
  as 
  previously 
  stated, 
  the 
  precaution 
  was 
  

   not 
  taken 
  to 
  repeat 
  the 
  fusion 
  with 
  sodium 
  carbonate 
  and 
  silica 
  

   in 
  estimating 
  that 
  constituent. 
  The 
  ratio 
  obtained 
  by 
  Damour 
  

   and 
  Deville 
  agrees 
  with 
  those 
  obtained 
  from 
  the 
  new 
  analyses 
  

   except 
  as 
  regards 
  fluorine. 
  It 
  is 
  believed, 
  however, 
  that 
  their 
  

   method 
  of 
  estimating 
  fluorine 
  is 
  open 
  to 
  criticism, 
  since 
  they 
  

   made 
  no 
  direct 
  determination 
  of 
  this 
  element 
  but, 
  assuming 
  

   that 
  on 
  dissolving 
  the 
  mineral 
  in 
  very 
  dilute 
  hydrochloric 
  acid 
  

   the 
  fluorine 
  separated 
  out 
  completely 
  as 
  the 
  fluorides 
  of 
  calcium 
  

   and 
  cerium, 
  they 
  ascertained 
  the 
  weight 
  of 
  these 
  fluorides, 
  and 
  

   considered 
  fluorine 
  as 
  equal 
  to 
  the 
  difference 
  between 
  this 
  

   weight 
  and 
  that 
  of 
  the 
  calcium 
  and 
  cerium 
  derived 
  from 
  an 
  

   analysis 
  of 
  the 
  insoluble 
  residue. 
  

  

  Excepting 
  the 
  defects 
  in 
  the 
  analyses, 
  evidently 
  due 
  to 
  fail- 
  

   ures 
  in 
  estimating 
  fluorine 
  correctly, 
  the 
  ratios 
  derived 
  from 
  

   the 
  three 
  analyses 
  indicate 
  conclusively 
  that 
  COj, 
  F, 
  (Ce, 
  La, 
  

   Y>\)fi^ 
  and 
  CaO 
  are 
  united 
  in 
  the 
  proportion 
  of 
  3:2:1:1. 
  

   Representing 
  the 
  trivalent 
  metals 
  of 
  the 
  cerium 
  group 
  collec- 
  

   tively 
  by 
  H, 
  it 
  is 
  probable 
  that 
  fluorine 
  is 
  directly 
  united 
  with 
  

   them 
  to 
  form 
  a 
  bivalent 
  radical 
  (RF), 
  and 
  that 
  parisite 
  is 
  a 
  

   double 
  carbonate, 
  2(RF)C03 
  + 
  CaC03, 
  or 
  (RF),Ca(C03)3. 
  ^ 
  

  

  As 
  far 
  as 
  the 
  proportions 
  of 
  the 
  different 
  constituents 
  is 
  con- 
  

   cerned, 
  either 
  of 
  the 
  foregoing 
  expressions 
  is 
  equivalent 
  to 
  the 
  

   formula 
  proposed 
  by 
  Grothf 
  (CaF)XCeF)';Ce(C03)3. 
  Groth 
  

   based 
  his 
  formula 
  upon 
  the 
  single 
  analysis 
  of 
  Damour 
  and 
  

   Deville, 
  previously 
  cited, 
  and 
  was 
  correct 
  in 
  assuming 
  that 
  the 
  

   deflciency 
  in 
  fluorine 
  was 
  due 
  to 
  a 
  failure 
  to 
  estimate 
  that 
  con- 
  

   stituent 
  correctly. 
  It 
  seems 
  to 
  us 
  more 
  reasonable 
  to 
  consider 
  

   the 
  fluorine 
  as 
  playing 
  a 
  single 
  role, 
  united 
  with 
  the 
  Ce, 
  La, 
  

   and 
  Di 
  metals 
  to 
  form 
  a 
  bivalent 
  radical 
  (RF), 
  than 
  to 
  adopt 
  

   the 
  formula 
  of 
  Groth 
  where 
  fluorine 
  plays 
  a 
  double 
  role, 
  united 
  

   with 
  calcium 
  to 
  form 
  a 
  univalent 
  radical 
  (CaF) 
  and 
  with 
  cerium 
  

   to 
  form 
  a 
  bivalent 
  i-adical 
  (CeF). 
  

  

  * 
  Tabellarische 
  Uebersicht 
  der 
  Mineralien, 
  1898, 
  p. 
  61. 
  

  

  Laboratory 
  of 
  Mineralog^y 
  and 
  Pelrog:rapliy, 
  

  

  Sheffield 
  Scientific 
  Scliool, 
  April, 
  1899. 
  

  

  