rochleder's  proximate  analysis. 
567 
for  the  presence  of  orgfinic  bases  and  copulated  compounds  in  the  same 
manner  as  described  for  the  crystals,  which  sometimes  are  deposited  from 
the  watery  decoction  after  treatment  with  sugar  of  lead,  subacetate  of 
lead,  and  sulphuretted  hydrogen,  and  evaporation.  As  neither  all  color- 
ing matters  nor  all  bitter  principles  and  organic  bases  are  retained  by 
animal  charcoal  when  their  watery  solutions  are  placed  in  contact  with  it, 
a  separation  of  two  coloring  matters,  two  bases,  or  two  bitter  principles,  can 
often  be  effected  by  charcoal,  which  can  only  with  diflBculty  be  accom- 
plished in  other  ways. 
The  further  examination  for  the  presence  of  organic  alkaloids,  copulated 
carbohydrates  and  indifferent  organic  compounds,  is  now  undertaken  in  the 
manner,  just  now  described  for  the  crystals,  with  those  portions  which  had 
been  absorbed  by  and  were  redissolved  from  charcoal,  and  with  those  bodies 
which  remain  dissolved  in  alcoholic  ether,  and  which  were  precipitated 
by  ether  from  the  alcoholic  solution. 
In  most  parts  of  plants  sugar  is  contained  which  passes  into  the  decoc- 
tion by  boiling  with  water.  It  is  neither  precipitated  by  sugar  of  iead  nor 
subacetate  of  lead,  and  therefore  remains  dissolved  in  the  fluid  which  has  been 
filtered  from  the  precipitate,  and  freed  from  lead  by  sulphuretted  hydrogen, 
and  concentrated  by  evaporation.  As  this  residue  always  contains  acetic 
acid  in  rather  considerable  quantity,  derived  from  the  employment  of  the 
acetates,  the  sugar  never  crystallizes  out.  At  least  I  have  never  obtained 
sugar  in  this  way.  By  treating  this  residue  with  alcohol  the  sugar 
dissolves  therein,  and  the  acetic  acid  likewise  goes  over  to  the  alcohol. 
On  the  addition  of  much  ether,  the  sugar  separates  from  the  acetous 
alcoholic  solution  us  a  heavy  layer  like  turpentine  at  the  bottom  of  the 
vessel,  and  adheres  to  its  sides  as  a  gummy  covering.  With  the  sugar, 
under  some  conditions,  other  bodies  may  be  precipitated.  On  that  account, 
the  impure  sugar  is  dissolved  in  alcohol,  and  mixed  with  a  strong  solution 
of  potash.  The  sugar  compound  of  the  potash  separates,  and  most  of  the 
other  substances  remain  dissolved  in  the  alcohol  containing  potash.  Whe- 
ther cane  sugar  or  grape  sugar  is  contained  in  the  watery  decoction  is  not 
ascertained  by  this  method  of  proceeding.  This  may  be  less  easily  dis- 
covered  by  the  treatment  of  the  watery  decoction  than  by  the  examination 
of  the  spirituous  extract  of  the  material  under  examination.  Of  this 
matter  we  shall  speak  further  on. 
It  must  be  observed  here,  that  alcohol  will  take  up  almost  always  the 
organic  bases  or  their  acetates,  as  well  as  the  copulated  carbohydrates,  from 
the  residue  of  the  aqueous  decoction,  left  after  its  treatment  with  acetate 
and  subacetate  of  lead  and  sulphuretted  hydrogen.  Such  bodies  are  only 
in  exceptional  cases  found  in  that  portion  not  dissolved  by  alcohol ;  but 
are  frequently  precipitated  by  ether  from  their  alcoholic  solution,  and  are 
then  in  most  cases  intermixed  with  sugar. 
Very  frequently  a  body  is  contained  in  the  alcoholic  extract  of  the  rcsi- 
