448  The  Detection  of  Em 0 din-Bearing  Drugs.  {\tJ0°buer;  f9urm' 
other  sufficiently  to  positively  identify  the  source  of  the  drug,  yet 
they  should  prove  of  considerale  value  as  confirmatory  evidence.  The 
light  red  from  senna  would  not  ordinarily  be  mistaken  for  the  deeper 
red  of  cascara  or  of  rhubarb,  nor  the  faint  reddish-yellow  of  aloes  for 
any  of  the  others,  particularly  if  controls  be  carried  out.  In  some 
instances,  on  standing,  a  reddish,  flocculent  precipitate  was  formed 
in  the  alkaline  solutions  as  finally  obtained.  On  its  removal  by  filtra- 
tion the  filtrate  became  lighter  in  color.  In  the  test  with  the  aloes- 
phenolphthalein  mixtures  the  filtrate  became  of  a  reddish-yellow 
color.  On  the  whole  the  test  is  much  less  satisfactory  for  aloes  than 
for  the  other  drugs  tested. 
While  these  experiments  were  in  progress  Bailey  5  published  a 
method  of  distinguishing  chrysophanic  acid  of  rhubarb  from 
phenolphthalein.  By  his  method  the  dealcoholized,  faintly  acidified 
preparation  is  shaken  with  ether,  and  the  solvent  layer  washed  with 
very  dilute  ammonia  water.  The  alkaline  solution  is  allowed-  to 
stand  over  night,  by  which  the  colored  compounds  of  haematoxylon 
and  curcuma,  if  present,  fade.  The  solution  is  then  acidified  and 
shaken  with  ether.  Only  chrysophanic  acid  and  phenolphthalein  pass 
into  the  solvent.  The  ether  is  evaporated  and  the  residue  boiled  with 
zinc  dust  and  potassium  hydroxide  solution  until  the  red  color  has 
entirely  disappeared.  By  this  treatment  chrysophanic  acid  is  reduced, 
*he  solution  becoming  yellowish,  and  phenolphthalein  is  reduced  to 
phenolphthalin.  The  solution  is  diluted  with  water,  or  a  drop  of 
hydrogen  peroxide  solution  is  added.  A  cherry-red  color  appearing 
at  once  indicates  chrysophanic  acid.  Under  these  conditions  phenol- 
phthalin is  not  oxidized. 
Bailey  did  not  apply  his  method  to  cascara  or  to  aloes,  but  implies 
that  it  might  be  used  on  senna  preparations.  We  have  applied  the 
method  to  the  fluidextracts  of  senna  and  cascara,  to  each  of  which 
some  alcoholic  solution  of  phenolphthalein  had  been  added.  In  each 
case  the  result  was  satisfactory.  It  was  found  necessary  to  boil  the 
alkaline  zinc-dust  mixture  for  some  time  in  order  to  completely 
destroy  the  red  color.  It  was  also  found  that  exposure  of  the  boiled 
solution  to  the  air,  as  in  filtration,  was  generally  sufficient  to  restore 
the  color  to  the  substance.  When  the  test  was  applied  to  Barbadoes 
aloes  1?he  red  color  given  on  the  addition  of  hydrogen  peroxide  solu- 
tion was  slow  to  appear  and  was  masked  considerably  by  yellow  color- 
ing matters.    To  the  limited  extent  that  comparison  tests  have  been 
5  Jour.  Ind.  Eng.  Chem.,  6,  320  (1914). 
