﻿484 
  DR 
  GEORGE 
  WILSON 
  ON 
  NEW 
  PROCESSES 
  FOR 
  FLUORINE, 
  &c. 
  

  

  The 
  processes 
  at 
  present 
  in 
  use 
  for 
  the 
  separation 
  of 
  fluorine 
  from 
  silica, 
  are 
  

   in 
  many 
  respects 
  satisfactory 
  ; 
  but 
  they 
  imply 
  the 
  rejection 
  of 
  glass 
  apparatus, 
  

   and 
  the 
  use 
  of 
  vessels 
  of 
  platina, 
  which, 
  from 
  their 
  costliness, 
  cannot 
  be 
  employed 
  

   of 
  any 
  considerable 
  size, 
  and, 
  from 
  their 
  opacity, 
  render 
  the 
  observation 
  of 
  phe- 
  

   nomena 
  occurring 
  within 
  them 
  impossible. 
  They 
  are 
  thus 
  inadmissible 
  for 
  opera- 
  

   tions 
  where 
  large 
  quantities 
  of 
  material 
  must 
  be 
  dealt 
  with 
  ; 
  and 
  to 
  the 
  impossi- 
  

   bility 
  of 
  employing 
  glass 
  and 
  porcelain 
  vessels, 
  must 
  be 
  largely 
  attributed 
  the 
  

   comparatively 
  limited 
  extent 
  of 
  our 
  information 
  as 
  to 
  the 
  distribution 
  of 
  fluorine. 
  

  

  The 
  following 
  processes, 
  which, 
  in 
  the 
  meanwhile, 
  are 
  offered 
  only 
  as 
  qualita- 
  

   tive 
  (although 
  I 
  hope 
  to 
  succeed 
  in 
  rendering 
  the 
  second 
  of 
  them 
  quantitative), 
  

   may 
  be 
  carried 
  on 
  in 
  the 
  ordinary 
  glass 
  and 
  porcelain 
  vessels 
  of 
  the 
  laboratory, 
  and 
  

   admit 
  of 
  everything 
  visible 
  being 
  observed. 
  They 
  are 
  applicable 
  to 
  all 
  siliceous 
  

   compounds 
  or 
  mixtures 
  containing 
  fluorine, 
  provided 
  it 
  be 
  present 
  in 
  the 
  form 
  of 
  a 
  

   fluoride 
  which 
  admits 
  of 
  decomposition 
  by 
  oil 
  of 
  vitriol 
  at 
  its 
  boiling 
  point. 
  The 
  

   first 
  stage 
  of 
  the 
  process 
  consists, 
  in 
  both 
  cases, 
  in 
  heating 
  the 
  silicated 
  fluoride 
  

   in 
  a 
  flask 
  along 
  with 
  strong 
  sulphuric 
  acid, 
  so 
  as 
  to 
  occasion 
  the 
  evolution 
  of 
  the 
  

   fluoride 
  of 
  silicon, 
  Si 
  F 
  3 
  . 
  This 
  gas 
  is 
  conducted 
  by 
  a 
  bent 
  tube 
  into 
  water, 
  where 
  

   it 
  deposits 
  a 
  portion 
  of 
  gelatinous 
  silica 
  ; 
  and 
  the 
  liquid, 
  after 
  filtration 
  (which, 
  

   however, 
  is 
  not 
  essential), 
  is 
  treated 
  as 
  follows 
  : 
  — 
  

  

  In 
  the 
  first 
  process, 
  I 
  adopted 
  one 
  of 
  Berzelius' 
  well-known 
  methods 
  for 
  the 
  

   isolation 
  of 
  silicon. 
  The 
  filtered 
  liquid 
  was 
  neutralised 
  with 
  potass 
  : 
  and 
  the 
  

   resulting 
  gelatinous 
  precipitate 
  of 
  fluoride 
  of 
  silicon 
  and 
  potassium 
  (2 
  Si 
  F„ 
  + 
  3 
  KF), 
  

   after 
  being 
  washed, 
  was 
  dried, 
  and 
  transferred 
  to 
  a 
  small 
  metallic 
  crucible, 
  in 
  

   which 
  it 
  was 
  heated 
  with 
  potassium, 
  so 
  as 
  to 
  separate 
  and 
  set 
  free 
  the 
  silicon, 
  

   and 
  convert 
  the 
  whole 
  of 
  the 
  fluorine 
  into 
  fluoride 
  of 
  potassium. 
  This 
  fluoride 
  

   was 
  then 
  dissolved 
  out 
  by 
  Avater, 
  evaporated 
  to 
  drjmess, 
  and 
  treated 
  in 
  the 
  ordi- 
  

   nary 
  way 
  with 
  oil 
  of 
  vitriol, 
  so 
  as 
  to 
  evolve 
  hydrofluoric 
  acid, 
  which 
  could 
  be 
  

   made 
  to 
  record 
  its 
  evolution 
  by 
  the 
  etching 
  which 
  its 
  vapour 
  occasioned 
  on 
  a 
  

   plate 
  of 
  waxed 
  glass, 
  with 
  lines 
  written 
  on 
  it 
  through 
  the 
  wax. 
  

  

  This 
  process 
  is 
  necessarily 
  tedious, 
  and 
  is 
  liable 
  to 
  several 
  objections. 
  The 
  

   most 
  serious 
  of 
  these 
  is 
  the 
  impossibility 
  of 
  effecting 
  the 
  complete 
  decomposition 
  

   of 
  the 
  fluoride 
  of 
  silicon 
  and 
  potassium, 
  by 
  potassium, 
  so 
  as 
  to 
  liberate 
  the 
  whole 
  

   of 
  the 
  silicon 
  ; 
  and 
  the 
  risk 
  of 
  the 
  latter 
  undergoing 
  oxidation 
  into 
  silica 
  during 
  

   the 
  washing 
  of 
  the 
  ignited 
  mass. 
  Accordingly, 
  though 
  this 
  method 
  gives 
  good 
  

   results, 
  and 
  has 
  enabled 
  me 
  to 
  detect 
  fluorine 
  in 
  coal, 
  in 
  which 
  I 
  could 
  not 
  pre- 
  

   viously 
  detect 
  more 
  than 
  the 
  faintest 
  traces 
  of 
  it, 
  yet 
  it 
  almost 
  unavoidably 
  neces- 
  

   sitates 
  a 
  loss 
  of 
  the 
  element 
  in 
  question, 
  and 
  is 
  much 
  inferior 
  in 
  simplicity 
  and 
  

   certainty 
  to 
  the 
  process 
  which 
  I 
  am 
  about 
  to 
  describe. 
  

  

  In 
  the 
  second 
  process, 
  as 
  in 
  the 
  first, 
  the 
  substance 
  under 
  examination 
  is 
  

   heated 
  with 
  oil 
  of 
  vitriol 
  so 
  as 
  to 
  yield 
  fluoride 
  of 
  silicon, 
  which 
  is 
  conducted 
  into 
  

   water. 
  The 
  resulting 
  solution 
  (with 
  or 
  without 
  filtration) 
  is 
  neutralised 
  with 
  

  

  