Am.  Jour.  Pliarm., 
Dec,  1885. 
Chemistry  of  Rhubarb, 
615 
means  of  petroleum  spirit  twice  with  94  per  cent,  alcohol,  and  allow- 
ing the  hot  filtered  liquor  to  evaporate  spontaneously,  when  no  chrys- 
ophanic  acid,  either  in  the  crystalline  or  the  amorphous  condition  will 
be  found  to  separate.  But  if  this  experiment  be  varied,  so  that  rhu- 
barb powder,  in  which  chrysophanic  acid  cannot  be  detected  by  the 
above  method,  be  first  macerated  with  water  forty-eight  hours,  the 
residue  filtered  oft  and  dried,  and  then  shaken  with  petroleum  spirit, 
the  interesting  observation  will  be  made  that  the  petroleum  spirit 
immediately  becomes  intensely  yellow.  Further,  if  a  rhubarb  powder 
thus  previously  treated  with  water  be  boiled  with  alcohol^  and  the  hot 
filtered  extract  allowed  to  evaporate  spontaneously  in  a  porcelain  dish, 
a  not  inconsiderable  quantity  of  chrysophanic  acid  will  separate  out, 
partially  amorphous  and  j^art  in  a  granular  crystalline  condition. 
In  illustration  of  this  statement  the  following  experiments  may  be 
quoted.  They  were  made  with  two  sorts  of  Chinese  rhubarb  which 
were  supplied  in  1878  and  1879  from  the  Crown  warehouse  in 
Warsaw  to  the  hospitals  of  the  Wilna  military  district  (I  and  II), 
and  with  a  crown  rhubarb  in  powder,  for  which  the  author  was 
indebted  to  Professor  Trapp. 
1.  Estimation  of  moisture  made  between  100°  and  105°C. 
1"006  gram  of  No.  I  lost  0"073  gram  =  7'26  per  cent. 
r013  gram  of  No.  II  lost  0'077  gram  =  7'70  per  cent. 
0-982  gram  of  No.  Ill  lost  0*079  gram  =  8  04  per  cent. 
2.  A  gram  of  each  kind  was digested  eight  days  with  twelve  grams 
of  light  petroleum  spirit  at  the  ordinary  temperature,  with  agitation. 
In  all  these  cases  the  supernatant  liquid  remained  perfectly  colorless, 
and  upon  evaporation  not  a  trace  of  chrysophanic  acid,  but  only  a 
small  quantity  of  a  soft  fatty  mass,  was  left. 
3.  Each  gram  of  rhubarb  was  placed  with  sixteen  grams  of  96° 
alcohol  in  a  small  retort  provided  with  a  return  condenser,  and  main- 
tained at  the  boiling  temperature  three  minutes.  The  liquid  was  then 
filtered  off",  and  the  residual  rhubarb  heated  to  boiling  with  eight 
grams  of  fresh  alcohol,  the  liquid  again  filtered  oft*,  and  the  united 
extracts  left  to  evaporate  spontaneously  in  a  porcelain  dish.  In 
neither  case  was  there  a  separation  of  a  trace  of  chrysophanic  acid. 
4.  One  gram  of  No.  I  was  macerated  forty-eight  hours  with  20  cc. 
of  distilled  water,  with  agitation ;  after  filtration  the  residue  was 
worked  upon  the  filter  with  13  cc.  of  water,  dried  at  about  30°C.,  and 
rubbed  down  in  an  agate  mortar. 
