rochleder's  proximate  analysis. 
371 
hy  sulphuretted  hydrogen,  and  filtered  from  sulphuret  of  lead,  is,  after  the 
expulsion  of  the  sulphuretted  hydrogen,  concentrated  by  evaporation  until 
the  residue  has  a  thin  syrupy  consistence.  A  small  portion  of  this  resi- 
due is  examined,  to  learn  whether  the  addition  of  alcohol  precipitates  sub- 
stances or  not.  If  by  the  addition  of  alcohol  at  ordinary  temperatures,  or 
after  heating  in  a  water-bath,  a  precipitate  is  developed,  the  whole  residue  is 
treited  with  alcohol,  and  the  alcoholic  liquid  filtered  from  the  precipitate.  It 
is  then  ascertained  whether  the  alcoholic  fluid  from  the  precipitate  when 
such  was  obtained  gives  or  not  a  precipitate  on  the  addition  of  ether.  In 
this  case  frequently  a  precipitate  results  of  a  semi-fluid  character.  Sugar, 
which  often  exists  in  parts  of  plants,  is  separated  by  treatment  with  ether. 
The  precipitate  sometimes  formed  by  alcohol  is  dissolved  in  the  smallest 
possible  quantity  of  water,  and  it  is  observed  whether  by  long  standing 
crystals  separate  or  not.  Exactly  in  the  same  manner,  the  precipitate 
caused  by  ether  is  treated.  From  the  fluid  containing  ether  and  alcohol 
by  a  gentle  heat  the  ether  as  well  as  the  alcohol  is  expelled,  and  the 
watery  residue  reserved  to  observe  if  crystals  form  therein  or  not. 
These  are  the  examinations  which  are  performed  with  a  portion  of  the 
fluid  which  has  been  obtained  by  the  treatment  of  the  watery  decoction 
with  sugar  of  lead,  subacetate  of  lead,  and  sulphuretted  hydrogen. 
Another  portion  of  this  fluid,  after  a  suitable  concentration,  is  allowed  to 
stand  for  a  long  time,  to  ascertain  whether  crystals  will  form  or  not  therein. 
Frequently  a  separation  of  crystals  takes  place  in  greater  or  less  quantity. 
If  such  crystals  form,  they  are  separated  from  the  dense  mother  liquor  by 
a  moist  linen  filter  on  a  glass  funnel.  The  upper  pai't  of  the  filter  is  af- 
terwards closed  by  means  of  a  thread,  and  laid  between  bibulous  paper,- 
and  pressed  upon  by  a  small  board  with  weights,  which  are  gradually  in- 
creased to  increase  the  pressure.  The  mother  liquid  separated  from  the  crys- 
tals contains,  besides  other  bodies,  always  a  greater  or  less  quantity  of  the 
crystalline  substance,  according  to  its  degree  of  solubility,  which,  upon 
a  closer  examination  of  the  mother  liquid,  must  be  taken  into  account. 
This  closer  examin  ition  v/ill  be  spoken  of  further  on. 
A  second  portion  of  the  watery  decoction  is  treated  with  animal  charcoal.' 
A  glass  tube,  about  half  an  inch  wide  and  eight  or  ten  inches  long,  is 
taken,  which  should  be  drawn  to  a  point  at  one  end.  The  mouth  of  the 
point  must  be  about  the  size  of  a  hempseed.  Into  the  wide  end  of  the 
tube  a  piece  of  loose  cotton  wool  is  introduced  and  pushed  into  the  pointed 
end  of  the  tube,  v/hich  is  fastened  vertically  in  a  clamp,  with  the  narrow 
mouth  downwards.  The  tube  is  filled  six  or  seven  inchea  high  with  pure 
animal  charcoal,  and  the  watery  decoction  is  poured  in  by  the  aid  of  a 
small  funnel  inserted  in  the  upper  mouth  of  the  tube.  The  fluid,  as  it 
passes  through  the  tube  into  a  glass  flask,  is  replaced  in  the  same  manner 
by  a  fresh  portion.  Coloring  and  bitter  principles  are  taken  up  frequently 
by  the  animal  charcoal  from  the  watery  decoction,  so  that  the  color  and 
the  taste  of  the  escaping  fluid  are  often  very  different  from  the  color  and 
