﻿DESTRUCTIVE 
  DISTILLATION 
  OF 
  ANIMAL 
  SUBSTANCES. 
  259 
  

  

  which 
  would 
  enable 
  us 
  to 
  understand 
  why 
  they 
  differ 
  from 
  the 
  aniline 
  series, 
  

   which 
  we 
  know 
  to 
  be 
  amidogen 
  bases. 
  If, 
  however, 
  they 
  belong 
  to 
  either 
  of 
  these 
  

   classes, 
  they 
  must 
  differ 
  remarkably 
  from 
  any 
  of 
  those 
  hitherto 
  examined^ 
  all 
  

   already 
  formed 
  being 
  extremely 
  unstable, 
  and 
  decomposed 
  even 
  by 
  very 
  feeble 
  

   affinities, 
  while 
  picoline 
  and 
  its 
  congeners 
  are 
  extremely 
  stable, 
  and 
  resist 
  even 
  

   the 
  action 
  of 
  nitric 
  acid. 
  Into 
  these 
  points, 
  however, 
  I 
  shall 
  not 
  now 
  enter, 
  but 
  

   reserve 
  their 
  discussion 
  for 
  a 
  future 
  part 
  of 
  this 
  paper. 
  

  

  Pyrrol 
  Bases. 
  

  

  I 
  have 
  already 
  referred, 
  at 
  the 
  commencement 
  of 
  this 
  paper, 
  to 
  another 
  series 
  

   of 
  bases, 
  to 
  which 
  I 
  have 
  given 
  the 
  provisional 
  name 
  of 
  pyrrol 
  bases, 
  and 
  which 
  

   distil 
  away 
  from 
  the 
  acid 
  fluid 
  by 
  which 
  the 
  others 
  are 
  retained. 
  They 
  are 
  

   obtained 
  in 
  the 
  form 
  of 
  an 
  oil, 
  which 
  is 
  transparent 
  and 
  colourless 
  at 
  the 
  moment 
  

   of 
  distillation, 
  but 
  rapidly 
  acquires 
  first 
  a 
  rose, 
  then 
  a 
  reddish-brown, 
  and 
  finally 
  

   an 
  almost 
  black 
  colour, 
  and 
  the 
  mixture 
  gives, 
  with 
  hydrochloric 
  acid 
  and 
  a 
  piece 
  

   of 
  fir 
  wood, 
  the 
  purple-red 
  colour 
  which 
  Runge 
  describes 
  as 
  characteristic 
  of 
  

   pyrrol. 
  In 
  fact, 
  I 
  imagined 
  that 
  I 
  had 
  at 
  length 
  obtained 
  this 
  substance, 
  which 
  

   had 
  escaped 
  me 
  in 
  my 
  previous 
  experiments, 
  but 
  I 
  soon 
  found 
  that 
  the 
  product 
  

   was 
  really 
  a 
  mixture 
  of 
  several 
  different 
  bases. 
  When 
  distilled 
  with 
  the 
  thermo- 
  

   meter 
  it 
  began 
  to 
  boil 
  at 
  about 
  212°, 
  and 
  the 
  temperature 
  gradually 
  rose 
  to 
  above 
  

   370°, 
  and 
  during 
  the 
  whole 
  of 
  the 
  distillation 
  pretty 
  large 
  fractions 
  were 
  obtained 
  at 
  

   every 
  ten 
  degrees, 
  but 
  those 
  between 
  280° 
  and 
  310° 
  were 
  decidedly 
  larger 
  than 
  

   the 
  others. 
  These 
  oils 
  were 
  all 
  bases, 
  with 
  a 
  peculiar 
  and 
  disgusting 
  odour, 
  quite 
  

   different 
  from, 
  and 
  much 
  more 
  disagreeable 
  than, 
  that 
  of 
  the 
  picoline 
  series 
  of 
  

   bases. 
  They 
  all 
  acquire 
  colour 
  on 
  standing, 
  although 
  more 
  slowly 
  than 
  the 
  

   crude 
  oil. 
  These 
  substances 
  dissolve 
  easily 
  in 
  a 
  small 
  quantity 
  of 
  hydrochloric 
  

   acid, 
  and 
  give, 
  with 
  bichloride 
  of 
  platinum, 
  a 
  precipitate 
  which 
  is 
  at 
  first 
  yellow, 
  

   but 
  is 
  rapidly 
  converted 
  into 
  a 
  black 
  substance. 
  When 
  dissolved 
  in 
  an 
  excess 
  of 
  

   acid, 
  and 
  heated 
  along 
  with 
  it, 
  they 
  present 
  a 
  very 
  remarkable 
  character 
  ; 
  the 
  

   solution 
  at 
  a 
  certain 
  temperature 
  becomes 
  filled 
  with 
  red 
  flocks, 
  so 
  abundant 
  and 
  

   bulky, 
  that, 
  if 
  not 
  too 
  dilute, 
  the 
  fluid 
  becomes 
  perfectly 
  solid, 
  and 
  the 
  vessel 
  can 
  

   be 
  inverted 
  without 
  anything 
  escaping. 
  The 
  same 
  change 
  takes 
  place, 
  though 
  

   more 
  slowly, 
  in 
  the 
  cold, 
  and 
  the 
  substance 
  deposited 
  is 
  then 
  of 
  a 
  pale 
  orange- 
  

   colour, 
  but 
  becomes 
  darker 
  by 
  boiling 
  or 
  exposure 
  to 
  the 
  air. 
  When 
  this 
  substance 
  

   is 
  collected 
  on 
  a 
  filter, 
  washed, 
  and 
  dried, 
  it 
  forms 
  a 
  reddish-brown 
  and 
  very 
  

   light 
  and 
  porous 
  mass. 
  It 
  is 
  insoluble 
  in 
  water, 
  acids, 
  and 
  alkalies, 
  but 
  soluble 
  in 
  

   alcohol, 
  and 
  the 
  solution 
  on 
  evaporation 
  leaves 
  a 
  dark 
  resinous 
  mass. 
  When 
  

   subjected 
  to 
  dry 
  distillation, 
  it 
  leaves 
  a 
  bulky 
  charcoal, 
  while 
  an 
  exceedingly 
  dis- 
  

   gusting 
  oil 
  distils. 
  

  

  The 
  acid 
  fluid 
  which 
  has 
  been 
  separated 
  from 
  this 
  substance 
  by 
  filtration, 
  

   when 
  supersaturated 
  by 
  an 
  alkali, 
  evolves 
  the 
  odour 
  of 
  the 
  bases 
  of 
  the 
  picoline 
  

   vol. 
  xx. 
  part 
  ii. 
  4 
  a 
  

  

  