618 
Chemistr^y  of  Rhubarb. 
\m.  .Tour.  Pharm., 
Dec,  1885. 
extract  of  rhubarb  prepared  Avith  dilute  spirit — for  instance,  tincture 
of  rhubarb — will  deposit  from  time  to  time  a  precipitate,  which 
according  to  Clarke  consists  chiefly  of  chrysophanic  acid.  In  such  an 
extract  there  is,  besides  the  chrysophan  of  the  root,  a  part  also  of  the 
body  capable  of  acting  upon  it  as  a  ferment.  The  breaking  up  of  the 
glucoside  is  therefore  only  imperfectly  and  gradually  effected. 
In  a  watery  extract  of  rhubarb — and  consequently  in  all  the  official 
extracts  prepared  by  macerating  the  root  with  water  —  it  would 
appear  from  the  foregoing  experiments  that  only  a  little  chrysophan 
can  be  expected,  because  under  such  conditions  the  glucoside  under- 
goes decomposition.  This  agrees  with  the  experience  of  the  author  in 
a  previous  investigation,  when  he  obtained  not  more  than  0*6  or  0'7 
gram  of  chrysophan  from  420  grams  of  "crown''  or  good  Chinese 
rhul)arb.  On  the  other  hand,  all  the  separated  chrysophanic  acid  will 
be  found  after  the  maceration  in  the  residual  marc ;  the  residue  after 
the  preparation  of  extractum  rhei  could  therefore  be  profitably  used 
as  a  source  of  pure  chrysophanic  acid,  as  the  article  appearing  in 
commerce  is  not  generally  pure.  For  this  purpose  the  dried  and 
powdered  marc  should  be  heated  to  boiling  Avith  three  times  its 
weight  of  alcohol  of  at  least  90°  Tr.,  in  a  retort  provided  with  a 
return  condenser,  the  temperature  maintained  five  minutes,  the  liquor 
filtered,  the  residue  boiled  a  second  time  with  one-and-a-half  times  its 
weight  of  alcohol,  again  filtered,  and  the  united  filtrates  allowed  to 
stand  twenty-four  liours  in  ti.e  cold  in  a  stoppered  vessel.  A  large 
portion  of  the  chrysophanic  acid  will  separate  in  a  granular  crystal- 
line condition.  If  the  supernatant  liquid  be  decanted,  the  alcohol 
distilled  off  and  the  residue  treated  with  dilute  alcohol  (40°  to 
50°  Tr.),  in  which  chrysophanic  acid  is  insoluble,  a  fuither  quantity 
of  coloring  matter  may  be  obtained. 
According  to  recent  observations,  chrysophanic  acid  possesses- 
strongly  antiseptic  properties,  to  which  rhubarb  doubtless  owes  it& 
beneficial  action  in  catarrh  of  the  stomach,  indigestion,  etc.  These 
properties  belong  to  chrysophan  also,  but  to  a  more  intense  degree; 
because  it  may  be  expected  that  when  it  reaches  the  stomach  chryso- 
phanic acid  is  at  once  split  off  and  is  thus  brought  into  action  in  a 
nascent  condition.  It  would  seem  therefore  desirable  that  in  the 
official  preparations  this  substance  pertaining  to  the  active  constitu- 
ents of  rhubarb  root  should  be  present  in  its  integrity.  As  has  been 
shown,  in  many  preparations  of  rhubarb  little  or  no  chrysophan  is  to- 
