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  XXV. 
  — 
  On 
  Meconic 
  Acid, 
  and 
  some 
  of 
  its 
  Derivatives. 
  By 
  Mr 
  Henry 
  How, 
  

   Assistant 
  to 
  Dr 
  Anderson. 
  Communicated 
  by 
  Dr 
  T. 
  Anderson. 
  

  

  (Read 
  5th 
  January 
  1852.) 
  

  

  In 
  a 
  paper 
  on 
  Comenic 
  Acid, 
  read 
  before 
  this 
  Society 
  in 
  April 
  of 
  last 
  year, 
  and 
  

   since 
  honoured 
  with 
  a 
  place 
  in 
  its 
  Transactions, 
  I 
  mentioned 
  my 
  being 
  engaged 
  

   in 
  an 
  investigation 
  on 
  Meconic 
  Acid 
  ; 
  the 
  details 
  of 
  the 
  experiments 
  referred 
  to 
  

   form 
  the 
  matter 
  of 
  the 
  present 
  communication. 
  

  

  My 
  object 
  in 
  undertaking 
  this 
  subject 
  was 
  to 
  ascertain 
  if 
  products 
  correspond- 
  

   ing 
  to 
  those 
  described 
  as 
  derived 
  from 
  comenic 
  acid 
  were 
  formed 
  under 
  similar 
  

   circumstances 
  in 
  the 
  case 
  of 
  meconic 
  acid. 
  I 
  also 
  thought 
  it 
  probable, 
  that 
  as 
  the 
  

   former 
  is 
  itself 
  a 
  derivative 
  of 
  the 
  latter, 
  the 
  changes 
  undergone 
  by 
  meconic 
  acid 
  

   in 
  some 
  reactions, 
  would 
  be 
  found 
  to 
  result 
  in 
  substances 
  apparently 
  the 
  imme- 
  

   diate 
  derivatives 
  of 
  comenic 
  acid. 
  This 
  remark 
  refers 
  to 
  the 
  action 
  of 
  heat 
  on 
  

   meconate 
  of 
  ammonia 
  ; 
  and 
  it 
  will 
  be 
  seen 
  that 
  the 
  expectation 
  was 
  realised. 
  A 
  

   similar 
  result 
  was 
  found 
  in 
  other 
  instances, 
  where 
  it 
  had 
  not 
  been 
  anticipated. 
  

  

  The 
  experiments 
  I 
  am 
  about 
  to 
  detail 
  were 
  performed 
  in 
  the 
  laboratory 
  of 
  Dr 
  

   T. 
  Anderson. 
  

  

  The 
  process 
  employed 
  for 
  the 
  purification 
  of 
  meconic 
  acid 
  was 
  that 
  given 
  

   by 
  Gregory 
  in 
  his 
  " 
  Outlines," 
  excepting 
  that 
  ammonia 
  was 
  substituted 
  for 
  

   potass 
  as 
  the 
  solvent 
  of 
  the 
  crude 
  acid. 
  As 
  in 
  the 
  case 
  of 
  comenic 
  acid 
  the 
  vola- 
  

   tile 
  alkali 
  was 
  preferred, 
  because, 
  although 
  in 
  both 
  cases 
  a 
  great 
  deal 
  of 
  acid 
  

   remains 
  in 
  the 
  highly 
  coloured 
  mother 
  liquors, 
  from 
  which 
  it 
  can 
  only 
  be 
  reco- 
  

   vered 
  in 
  a 
  pure 
  state 
  at 
  the 
  expense 
  of 
  much 
  time 
  and 
  labour, 
  it 
  was 
  found 
  that 
  

   if 
  ammonia 
  was 
  used, 
  the 
  whole 
  of 
  the 
  mother 
  liquors 
  could 
  be 
  employed 
  under 
  

   circumstances 
  where 
  their 
  impure 
  state 
  did 
  not 
  affect 
  the 
  results 
  of 
  the 
  experi- 
  

   ment. 
  A 
  considerable 
  saving 
  was 
  thus 
  effected. 
  This 
  point 
  is 
  of 
  some 
  import- 
  

   ance, 
  because 
  the 
  numerous 
  solutions 
  requisite 
  for 
  the 
  purification 
  of 
  meconic 
  

   acid 
  occasion 
  so 
  much 
  loss, 
  that 
  seldom 
  much 
  more 
  than 
  a 
  fourth 
  part 
  of 
  the 
  

   weight 
  of 
  the 
  crude 
  acid 
  started 
  from, 
  is 
  obtained 
  as 
  the 
  result 
  of 
  a 
  careful 
  pre- 
  

   paration. 
  

  

  The 
  process 
  consists 
  in 
  dissolving 
  crude 
  meconic 
  acid 
  in 
  hot 
  water 
  by 
  aid 
  of 
  

   caustic 
  ammonia. 
  The 
  crude 
  acid 
  is 
  obtained 
  from 
  meconate 
  of 
  lime 
  by 
  treating 
  

   it 
  three 
  successive 
  times 
  with 
  twenty 
  parts 
  boiling 
  water 
  and 
  three 
  parts 
  strong- 
  

   muriatic 
  acid. 
  The 
  mixture 
  of 
  the 
  acid 
  so 
  obtained, 
  and 
  about 
  twice 
  its 
  weight 
  

   of 
  water, 
  is 
  kept 
  hot 
  in 
  a 
  water-bath 
  and 
  constantly 
  agitated, 
  till, 
  by 
  the 
  addition 
  

   of 
  caustic 
  ammonia, 
  solution 
  is 
  complete 
  ; 
  the 
  salt 
  formed 
  is 
  extremely 
  soluble 
  in 
  

   hot 
  water, 
  and 
  the 
  fluid 
  cools 
  to 
  a 
  solid 
  mass. 
  The 
  black 
  mother 
  liquor 
  is 
  squeezed 
  

  

  VOL. 
  XX. 
  PART 
  III. 
  5 
  Q 
  

  

  