bochledee's  proximate  analysis. 
179 
BO  far  as  they  are  soluble  in  water,  the  latter  the  volatile,  or  rather  the  con- 
stituents, distillable  with  water,  of  the  material.  For  the  treatment  of  the 
material  under  examination  with  water,  an  ordinary  still  is  required.  The 
still,  which  must  be  sufficiently  capacious,  is  filled  with  the  water  intended 
for  the  extraction  of  the  material,  and  this  is  heated  to  the  boiling  point. 
When  the  water  boils,  the  material  suitably  divided,  is  thrown  into  the 
water,  the  receiver  adjusted,  and  proper  care  taken  for  its  refrigeration. 
To  introduce  the  divided  material,  carefully  into  the  boiling  water,  and  to 
prevent  burning  as  much  as  possible,  I  employ  an  apparatus  which  I  will 
in  a  few  words  here  describe.  This  consists  of  a  cylinder,  open  at  the  top 
and  closed  at  the  bottom,  made  of  tinned  iron  plate.  The  sides  and  the 
bottom  of  the  cylinder  are  perforated  with  holes,  so  that  the  cylinder  rep- 
resents a  coarse  sieve.  Externally,  at  the  bottom,  three  short  feet  are  at- 
tached, and  a  cover  of  tinned  iron  plate,  likewise  perforated,  closes  the 
cylinder  in  which  it  is  inserted,  being  in  diameter  about  two  lines  less  than 
the  cylinder.  The  material  is  introduced  into  this  cylinder  without  being 
pressed,  and  the  cover  is  laid  on.  By  means  of  twine  the  cover  is  fastened 
to  the  place  where  it  lays.  The  size  of  the  cylinder  depends  upon  the  ca- 
pacity of  the  still.  In  filling  the  cylinder,  care  must  be  taken  that  the 
material  is  only  in  such  quantity  that  it  is  covered  at  least  three  inches 
high  by  the  water  in  the  still  when  the  cylinder  is  inserted  in  the  boiler, 
which  is  done  while  the  water  boils. 
When  the  material  is  thus  introduced  into  the  already  boiling  water,  the 
decomposing  action  of  ferments  contained  therein  on  the  other  constitu- 
ents is  prevented,  from  which  decomposition  products  would  be  produced, 
whose  formation  must  not  be  permitted.  We  know  by  the  treatment  de- 
scribed that  bitter  almonds  afibrd  no  bitter  almond  oil,  and  mustard  no  mus- 
tard oil.  It  is  of  importance  in  the  investigation  of  the  distillate  to  pre- 
vent the  formation  of  volatile  products  from  the  non-volatile  constituents 
of  the  material.  But  independently  of  the  volatile  decomposition  products 
Vfhich  could  be  formed  when  the  directions  mentioned  are  not  observed,  de- 
composition might  occur  which  would  give  rise  to  erroneous  ideas  of  the 
composition  of  the  substance  under  examination  in  the  investigation,  of 
its  watery  decoction,  because  there  are  in  many  plants  bodies,  besides  fer- 
ments, which  are  broken  up  into  two  or  more  non-volatile  products  when 
they  are  long  in  contact  with  water  and  ferments.  This  is  the  case  when 
the  material  is  placed  in  cold  water  and  then  heated  to  the  boiling  point, 
which  occupies  a  longer  time  the  greater  the  quantities  of  material  and 
water  that  are  to  be  raised  to  the  boiling  point.  The  root  of  the  rubia  tinc- 
torum  is  an  example  of  this  kind,  which  contains  a  peculiar  ferment  by 
which  ruberythric  acid  in  the  presence  of  a  ferment  is  decomposed  into  ali- 
zarine and  sugar,  when  the  comminuted  root  is  placed  in  cold  water  and  then 
heated  to  the  boiling  point.  On  the  contrary,  when  the  divided  root  is  in- 
troduced into  boiling  water,  the  ruberythric  acid  remains  unchanged  and 
