6i6 
The  CJiemistry  of  Rhubarb. 
(  Am.  Jour  Phartn. 
I    December,  1895. 
C15H10O4,  and  that  it  is  closely  related  to  emodin,  for  which  the 
formula  C15H10O5  was  deduced  by  Liebermann7  from  his  own  analy- 
ses, as  well  as  from  those  of  De  la  Rue  and  Miiller. 
According  to  Kubly,s  chrysophanic  acid  exists  only  in  very  small 
amount  in  fresh  rhubarb,  but  is  produced  by  the  alteration  of  a 
glucoside,  to  which  he  gave  the  name  of  chrvsophan.  Proctor9  has 
also  observed  a  formation  of  chrysophanic  acid  in  rhubarb  under  the 
influence  of  exposure  to  air  in  contact  with  water  and  caustic  alkali. 
SchrofT10  considers  that  chrysophanic  acid  is  the  active  principle 
of  rhubarb.  However,  the  substance  with  which  Schroff  operated 
was  not  the  chrysophanic  acid  of  rhubarb,  but  that  of  Physcia,  and, 
moreover,  it  was  not  pure.  On  the  other  hand,  v.  Auer11  experi- 
mented with  the  chrysophanic  acid  of  rhubarb,  and  found  that  it  had 
no  action  upon  the  intestinal  canal.  According  to  his  results,  the 
purgative  constituent  of  rhubarb  is  still  unknown. 
In  prefacing  the  account  of  my  investigation  with  these  remarks, 
I  must  also  state  that  it  was  undertaken  in  consequence  of  the 
observation12  that  the  composition  of  chrysophanic  acid  obtained 
from  Physcia  parietina  is  not  represented  by  the  formula  C15H10O4, 
which  has  been  found  by  Liebermann  and  Fischer  to  represent  the 
sublimed  chrysophanic  acid  of  rhubarb,  Rochleder's  statement 
that  the  chrysophanic  acid  of  rhubarb  loses  some  water  at  1 1 5  0  C, 
suggested  the  possibility  that  at  the  temperature  of  sublimation 
there  might  be  a  further  elimination  of  water,  and  that  the  sublimed 
substance  might  be  a  product  of  condensation.  It  appears,  how- 
ever, from  my  investigation  of  the  subject,  that  neither  the  state- 
ments of  Rochleder  and  Heldt  relating  to  the  composition  of  chry- 
sophanic acid  from  Physcia,  nor  those  of  Schlossberger  and  Dopping, 
De  la  Rue  and  Miiller,  or  Pilz  and  Rochleder,  in  reference  to  the 
chrysophanic  acid  of  rhubarb,  are  correct,  but  I  have  been  able  to 
confirm  the  results  of  Liebermann  and  Fischer.  Moreover,  the 
chrysophanic  acid  of  Physcia  is  not  identical  with  that  of  rhubarb, 
and  the  opinion  expressed  by  Schlossberger  and  Dopping  that  these 
' Berichte.,  8,  970. 
8JVeues  Rep.  fur  Pharm.,  it,  216. 
^ Pharm.  Journ.  [3],  25.  233. 
™Vierteljahresch.fur  Pharm.,  5,  269. 
nDe  Pad.  Rhei.    Dorpat,  1859. 
nLiebi%'  Annalen,  284,  177. 
