236 
ON  PYRODEXTRINE. 
he  adopted  the  conditions  most  suitable  for  obtaining  a  high  de- 
gree of  torrefaction,  that  is  to  say,  the  greatest  coloration  possi- 
ble. He  acted  quite  contrary  to  the  manufacturer  of  dextrine, 
who  moderates  the  action  of  heat  as  much  as  possible,  lest  his 
products  should  acquire  a  yellowish  tint  which  would  render  their 
sale  less  easy. 
He  begins  the  torrefaction  in  a  flat-bottomed  basin,  heated  at 
one  end ;  the  fecula  is  placed  at  one  end ;  it  first  loses  all  its 
hygrometric  water,  is  converted  into  dextrine,  and  begins  to  be- 
come colored.  Then,  the  heat  continuing  its  action,  this  dex- 
trine undergoes  a  kind  of  igneous  fusion ;  it  swells  up,  and  it 
then  becomes  easy  to  separate  this  half-fused  matter  from  the 
bottom  of  the  basin,  by  means  of  an  iron  spatula,  under  the  form 
of  strips,  which  are  broken  on  cooling.  These  strips  are  pushed 
into  the  cooler  parts  of  the  basin,  and  the  hot  parts  are  covered 
with  fecula,  the  torrefaction  of  which  is  not  so  far  advanced. 
By  continuing  this  plan  for  a  sufficient  length  of  time,  we 
ultimately  convert  all  the  fecula  into  fused  matter.  This  matter 
is  already  very  highly  colored. 
In  order  to  reach  the  fecula  and  dextrine,  which,  imprisoned 
in  the  fused  mass,  have  escaped  torrefaction,  the  product  is 
heated  with  water,  the  burnt  and  insoluble  portions  are  separated 
by  decantation,  and  the  liquor  is  evaporated  to  the  consistence 
of  an  extract.  This  extract  is  divided  into  small  masses,  which 
are  placed  in  the  drawer  of  an  aerothermal  furnace,  the  dessica- 
tion  is  first  completed,  and  then  the  torrefaction  is  finished  by 
keeping  the  matter  for  a  sufficient  length  of  time  at  230°  C. 
(446°  P.) 
His  final  product  occurs  under  the  appearance  of  light  spongy 
masses,  like  tannin,  unalterable  in  the  air,  easily  reduced  to 
powder  by  simple  pressure  between  the  fingers,  extremely  soluble 
in  water,  without  being  deliquescent,  and  furnishing  with  water 
a  deep  brown  solution.  This  matter,  when  the  operation  has 
been  well  conducted,  is  almost  entirely  formed  of  a  new  colored 
substance  which  M.  Gelis  has  called  pyrodextrine. 
This  substance  is  more  stable  than  the  different  products 
which  are  extracted  from  caramel :  thus,  it  is  not  necessary  for 
obtaining  it  in  the  pure  state  to  avoid  the  employment  of  acids 
and  bases  which  destroy  the  derivatives  of  sugar  with  such  facility. 
