rochleder's  proximate  analysis. 
465 
(Continufd  fiom  page  376.) 
the  water.    One  of  the  constituents  often  then  remains  in  the  form  of  mi- 
croscopic crystals  or  as  an  amorphous  powder,  at  least  for  a  short  time, 
undissolved,  and  can  be  separated  from  the  other  bodies  easily  and  quickly 
soluble  in  water  by  a  rapid  filtration. 
We  will  now  apply  our  attention  to  the  precipitates  which  are  thrown 
down  by  a  solution  of  alum  and  ammonia  from  a  portion  of  the  watery  de- 
coction. 
The  precipitate  washed  on  the  filter  with  water  is  treated  with  dilute  sul- 
phuric acid,  and  allowed  to  remain  some  time  in  contact  with  the  same,  ac- 
companied with  frequent  stirring.  For  this  purpose,  the  precipitate  on  the 
filter  is  introduced  into  a  capacious  glass  vessel.  The  solution  is  filtered 
from  the  portion  remaining  undissolved,  and  this  is  washed  on  a  filter  with 
water.  The  residue  washed  with  water  is  treated  with  hot  alcohol,  wherein 
such  substances  dissolve.  These  can  be  precipitated  from  the  alcoholic 
solution  by  loater,  and  after  being  washed  with  water,  may  be  preserved 
for  a  closer  examination  by  being  dried  in  vacuo  over  sulphuric  acid. 
The  solution  obtained  hy  the  application  of  dilute  sulphuric  acid  is  mixed 
with  a  saturated  solution  of  sulp>hate  of  poiassa,  whereby  the  alum  is  re- 
formed, and  at  the  same  time  is  partially  precipitated.  The  fluid  is  mixed 
with  anhydrous  alcohol  as  long  as  an  addition  of  the  same  produces  a  pre- 
cipitate of  alum  and  sulphate  of  potash,  and  the  spirituous  liquid  is  filtered 
from  the  precipitate.  The  quantity  of  sulphuric  acid  M-hich  is  still  present 
in  the  fluid  in  a  free  condition  is  separated  by  the  introduction  of  moist 
white  lead,  prepared  by  passing  carbonic  acid  into  subacetate  of  lead. 
The  sulphate  of  lead  is  separated  by  a  filter,  and  the  small  quantity  of  lead 
dissolved  removed  from  the  liquid  by  sulphuretted  hydrogen.  After  filter- 
ing ofi"  the  sulphuret  of  lead  and  expelling  the  sulphuretted  hydrogen,  the 
alcohol  is  distilled  ofi"  and  the  watery  residue  employed  for  further  investi- 
gation. It  is  self-evident  that  the  greatest  portion  of  the  substances  con- 
tained in  this  fluid  are  those  which  were  precipitated  by  sugar  of  lead  and 
subacetate  lead  from  a  portion  of  the  watery  decoction,  with  the  exception 
of  those  which  are  not  precipitated  with  alum,  or  remain  undissolved  by  the 
treatment  of  the  aluminous  precipitate  with  dilute  sulphuric  acid.  This 
fluid  is  therefore  treated  exactly  as  is  above  described  with  the  first  portion 
of  the  watery  decoction — namely,  with  sugar  of  lead  and  subacetate  of  lead, 
and  the  resulting  precipitates  are  examined  in  precisely  the  same  man- 
ner. 
It  was  mentioned  before  that  a  part  of  the  watery  decoction  was  to  be 
treated  with  animal  charcoal,  and  the  charcoal  washed  with  water  and  ex- 
tracted with  boiling  alcohol.  This  alcoholic  extract  may  contain  coloring 
matters,  indifierent  bitter  principles,  organic  bases,  &c.  After  its  evapora- 
tion, either  crystals  are  separated  which  can  be  removed  from  the  mother 
liquor,  or  no  crystals  are  formed.  The  whole  residue,  where  no  crystals 
have  separated,  or  the  mother  liquors  from  which  the  crystals  have  been 
30 
