«  m  Jour.  Pharm.  "> 
December,  1895.  / 
The  Chemistry  of  Rhubarb. 
617 
substances  were  identical,  may  be  ascribed  to  impurity  of  the  mate- 
rial in  their  hands. 
In  a  previous  paper  I  have  described  the  chrysophanic  acid  of 
Physcia  under  the  name  of  physcion,  and  as  having  a  composition 
represented  by  the  formula — 
C16H,A  =  C15H;02(OH)2  (OCH3). 
The  composition  of  the  chrysophanic  acid  of  rhubarb  is  represented 
by  the  formula — 
C,5H10O4  =  CI5H802(OH)2, 
and  I  propose  retaining  for  it  the  name  chrysophanic  acid,  although 
the  term  is  incorrect,  because  this  substance  does  not  possess  the 
characters  of  an  acid,  as  has  been  already  pointed  out  by  De  la  Rue 
and  Muller. 
The  material  operated  upon  in  this  investigation  was  Chinese 
rhubarb ;  one  pound  in  a  state  of  fine  powder  was  digested  with 
five  times  its  weight  of  ether  in  a  glass  flask,  and  frequently  shaken 
during  ten  days.  The  ether  solution  was  then  poured  off,  filtered 
and  distilled,  the  distillate  being  returned  to  the  partially  exhausted 
rhubarb.  By  repeating  this  treatment  several  times  until,  in  the 
course  of  three  months,  ten  successive  portions  of  extract  had  been 
obtained,  the  rhubarb  powder  was  still  only  imperfectly  extracted  ; 
it  had  a  grayish  yellow  color  and  became  red  upon  the  addition  of 
caustic  potash  solution,  probably  owing  to  the  presence  of  some 
rhei'n. 
The  somewhat  considerable  quantities  of  ether  extract  obtained 
as  residues  assumed  a  crystalline  condition  on  cooling.  When 
treated  with  cold  80  per  cent,  alcohol  a  dark  brown  solution  was 
formed,  and  a  pulverulent  crystalline  substance  remained  undis- 
solved. On  spontaneous  evaporation  the  solution  left  an  amorphous 
residue  containing  paler  colored  crystalline  particles  consisting  of 
crystals  of  a  colorless  substance  and  a  residue  of  chrysophanic 
acid.  These  crystals  could  be  separated  by  further  treatment  of  the 
residue  with  weak  alcohol,  and  in  that  way  a  solution  was  obtained 
which  left,  on  evaporation,  a  perfectly  amorphous  dark  brown  resi- 
due, possessing  in  a  high  degree  the  purgative  property  of  rhubarb. 
The  alcoholic  solution  of  this  substance  has  a  bitter  and  somewhat 
acrid  taste,  when  boiled  with  hydrochloric  acid  it  did  not  yield 
either  chrysophanic  acid  or  sugar.    This  extract  contained  almost 
