616 
Chemistry  of  Rhuharh. 
Am.  Jour.  Pharm., 
Dec,  1885. 
The  powder  thus  obtained  was  then  treated  exactly  as  that  in  exper- 
iment 3 ;  that  is,  boiled  with  alcohol  and  the  extract  allowed  to  evap- 
orate at  the  ordinary  temperature.  Already,  on  the  second  day,  a 
yellow  granular  precipitate  had  separated,  partly  upon  the  bottom  and 
sides  of  the  dish  and  partly  as  a  yellow  crystalline  skin  upon  the 
surface  of  the  liquid.  On  the  third  day,  after  the  complete  evapora- 
tion of  the  liquid,  the  yellowish  residue  in  the  dish  was  taken  up  with 
10  grams  of  40°  spirit,  filtered,  the  residue  washed  upon  the  filter 
with  6  grams  of  spirit  of  the  same  strength,  but  boiling,  in  order  to 
remove  impurities,  such  as  phseoretin,  erythioretin  and  fat,  and  then 
the  remainder,  together  with  the  filter,  dried  at  between  100°  and 
105°C.  The  w^eight  of  the  colored  matter  amounted  to  0*0196 
gram,  which  calculated  upon  the  dried  substance  represented  2*12  per 
cent.  It  was  of  a  golden  yellow  color,  presented  a  granular  crystal- 
lization, and  separated  readily  from  the  filter  after  drying.  It  behaved 
towards  reagents  and  solvents  exactly  like  chrysophanic  acid.  Never- 
theless, it  still  contained  traces  of  emodin,  which  could  be  demon- 
strated in  the  following  way.  The  colored  matter  was  treated,  as 
recommended  by  Rochleder,  with  boiling  soda  solution,  in  which 
chrysophanic  acid  is  insoluble,  the  solution  decomposed  with  hydro- 
chloric acid,  and  the  separated  flocks  collected  upon  a  filter,  washed, 
taken  up  in  a  little  liot  94°  alcohol  and  the  solution  left  to  evaporate 
to  about  one-third  of  its  volume  on  a  watch-glass.  Yellow  flocks 
were  then  found  to  have  separated,  which  brought  under  the  micro- 
scope by  means  of  a  glass  rod  proved  to  consist  of  agglomerations  of 
needles  grouped  in  a  stellate  arrangement  round  a  generally  darker 
eel  1  u  1  ar-for ed  u  ucleus. 
1"0236  gram  of  rhubarb  No.  II,  treated  in  exactly  the  same  way 
as  in  the  previous  experiment,  No.  4,  gave  0*098  gram  of  chryso- 
phanic acid  =  2*09  per  cent,  of  coloring  matter  in  the  dried  substance. 
1*0174  gram  of  rhubarb  No.  Ill  gave  0*0194  gram  of  chryso- 
phanic acid  =  2*07  per  cent,  in  the  dried  substance.  In  the  coloring 
matters  prepared  from  Nos.  II  and  III  also  distinct  traces  of  emodin 
could  be  detected. 
5.  1*0236  of  rhubarb  No.  II,  treated  exactly  as  in  experiment  4, 
only  with  the  difference  that  instead  of  forty-eight  hours  it  was 
macerated  with  water  twenty-four  hours,  gave  0*021  gram  of  coloring 
matter  =  2*21  per  cent,  in  the  dried  substance. 
It  will  be  seen  that  this  yield  was  somewhat  larger  than  that  from 
