﻿DR 
  GEORGE 
  WILSON 
  ON 
  NEW 
  PROCESSES 
  FOR 
  FLUORINE, 
  &c. 
  485 
  

  

  ammonia 
  instead 
  of 
  potass, 
  and 
  then 
  evaporated 
  to 
  dryness, 
  which 
  has 
  the 
  effect 
  

   of 
  rendering 
  the 
  silica 
  produced 
  insoluble. 
  On 
  digesting 
  water 
  on 
  the 
  residue, 
  

   fluoride 
  of 
  ammonium 
  is 
  dissolved, 
  and 
  the 
  solution 
  requires 
  only 
  to 
  be 
  evaporated 
  

   to 
  dryness 
  and 
  moistened 
  with 
  sulphuric 
  acid 
  to 
  give 
  off 
  hydrofluoric 
  acid, 
  which 
  

   readily 
  etches 
  glass. 
  The 
  stages 
  in 
  the 
  ammonia 
  process 
  are 
  thus 
  : 
  — 
  

  

  1st, 
  Distillation 
  of 
  the 
  substance 
  with 
  oil 
  of 
  vitriol, 
  so 
  as 
  to 
  produce 
  fluoride 
  of 
  

   silicon, 
  Si 
  F 
  3 
  . 
  

  

  2d, 
  Neutralisation 
  of 
  the 
  aqueous 
  solution 
  of 
  the 
  distillate, 
  with 
  ammonia 
  in 
  

   excess, 
  so 
  as 
  to 
  produce 
  fluoride 
  of 
  silicon 
  and 
  ammonium, 
  2 
  SiF 
  3 
  + 
  3 
  NH 
  4 
  F. 
  

  

  3d, 
  Evaporation 
  of 
  the 
  neutralised 
  liquid 
  to 
  dryness, 
  so 
  as 
  to 
  separate 
  silica, 
  

   and 
  render 
  it 
  insoluble. 
  

  

  4th, 
  Exhaustion 
  of 
  the 
  residue 
  with 
  water, 
  and 
  evaporation 
  to 
  dryness, 
  so 
  as 
  

   to 
  leave 
  fluoride 
  of 
  ammonium. 
  

  

  5th, 
  Moistening 
  of 
  the 
  ammonio-fluoride 
  with 
  oil 
  of 
  vitriol, 
  so 
  as 
  to 
  liberate 
  

   hydrofluoric 
  acid 
  ; 
  which 
  will 
  act 
  upon 
  glass. 
  

  

  I 
  have 
  tried 
  this 
  process 
  with 
  Aberdeen 
  and 
  Peterhead 
  granite 
  ; 
  with 
  three 
  

   trap 
  rocks 
  from 
  the 
  neighbourhood 
  of 
  Edinburgh, 
  namely, 
  basalt 
  from 
  Arthur 
  

   Seat, 
  greenstone 
  from 
  Corstorphine 
  Hill, 
  and 
  clinkstone 
  from 
  Blackford 
  Hill 
  ; 
  

   with 
  a 
  deposit 
  from 
  the 
  boiler 
  of 
  the 
  Atlantic 
  steamer, 
  Canada 
  ; 
  with 
  a 
  fossil 
  

   bone 
  ; 
  with 
  the 
  ashes 
  of 
  charcoal, 
  of 
  barley-straw, 
  and 
  of 
  hay 
  ; 
  and 
  in 
  all 
  with 
  such 
  

   success 
  that 
  the 
  applicability 
  of 
  the 
  process 
  to 
  the 
  end 
  proposed 
  is 
  certain. 
  The 
  

   pieces 
  of 
  glass, 
  etched 
  by 
  hydrofluoric 
  acid 
  evolved 
  from 
  the 
  substances 
  referred 
  

   to, 
  which 
  I 
  lay 
  upon 
  the 
  table, 
  are 
  not 
  selected 
  successful 
  specimens, 
  but 
  repre- 
  

   sent 
  the 
  whole 
  of 
  the 
  trials 
  made 
  by 
  the 
  ammonia 
  process. 
  The 
  etchings 
  on 
  the 
  

   majority 
  of 
  them 
  are 
  as 
  deep 
  as 
  could 
  be 
  obtained 
  from 
  pure 
  fluorspar 
  and 
  oil 
  of 
  

   vitriol 
  ; 
  and, 
  with 
  the 
  experience 
  which 
  I 
  have 
  now 
  acquired, 
  I 
  have 
  no 
  doubt 
  

   that 
  I 
  shall 
  be 
  more 
  successful 
  in 
  succeeding 
  trials 
  with 
  vegetable 
  ashes, 
  which, 
  

   for 
  reasons 
  to 
  be 
  presently 
  mentioned, 
  require 
  more 
  precautions 
  than 
  fragments 
  

   of 
  rock 
  do. 
  

  

  The 
  examination 
  of 
  a 
  hard 
  crystalline 
  mineral, 
  such 
  as 
  granite, 
  or 
  an 
  un- 
  

   weathered 
  trap, 
  presents 
  no 
  difficulties. 
  It 
  must 
  be 
  reduced 
  to 
  a 
  tolerably 
  fine 
  

   powder, 
  and 
  employed 
  in 
  considerable 
  quantity. 
  A 
  little 
  sulphurous 
  acid 
  is 
  

   always 
  evolved 
  during 
  the 
  action 
  of 
  the 
  oil 
  of 
  vitriol, 
  from 
  the 
  dust 
  which 
  is 
  

   gathered 
  during 
  a 
  protracted 
  process 
  of 
  powdering 
  ; 
  but 
  the 
  presence 
  of 
  this 
  acid 
  

   in 
  small 
  quantity 
  is 
  of 
  no 
  importance, 
  and 
  the 
  powdering 
  of 
  the 
  rock 
  is 
  the 
  most 
  

   troublesome 
  part 
  of 
  the 
  investigation. 
  

  

  It 
  is 
  otherwise 
  with 
  weathered 
  granite 
  and 
  trap, 
  which 
  containc 
  hlorides 
  and 
  

   carbonates, 
  and 
  give 
  off 
  hydrochloric 
  and 
  carbonic 
  acids 
  when 
  treated 
  with 
  sul- 
  

   phuric 
  acid. 
  These 
  gaseous 
  acids 
  materially 
  interfere 
  with 
  the 
  processes 
  described 
  

   by 
  the 
  frothing 
  which 
  they 
  occasion, 
  and 
  by 
  their 
  tendency 
  to 
  sweep 
  away 
  the 
  

   hydrofluoric 
  acid 
  which 
  may 
  accompany 
  them. 
  In 
  my 
  earlier 
  trials, 
  accordingly, 
  

  

  