44  Digitalis  Glue o sides  and  Allied  Drugs.  {  ^anJ™£  ^J10' 
green  and  the  acid  yellow.  The  mechanism  of  the  green  colora- 
tion has  not  yet  been  explained. 
While  digitoxin  produces  a  green  coloration  with  concentrated 
hydrochloric  acid,  it  causes  a  greenish-brown  to  brown  color  with 
iconcentrated,  pure  sulphuric  acid.  Digitalinum  verum,  on  the 
other  hand,  is  only  colored  yellow  by  sulphuric  acid.  But  if  the 
sulphuric  acid  contains  oxidizing  substances,  such  as  iron  oxide 
or  nitric  acid,  it  yields  a  deep  red  color  with  digitalinum  verum. 
For  this  reason  Grandeau  24  also  used  bromine  with  the  sulphuric 
acid  for  the  digitalin  reaction,  by  exposing  the  solution  of  digi- 
talin  in  sulphuric  acid  to  the  action  of  bromine  vapor.  In  carry- 
ing out  this  reaction  a  violet-red  color  is  obtained.  Buckingham  25 
used  a  solution  of  molybdic  acid  in  sulphuric  acid,  which  yields 
a  crimson  color  with  digitalin.  Kiliani  26  describes  a  digitalin 
reaction  similar  to  Grandeau's  which  is  probably  characteristic  of 
digitalinum  verum.  If  a  little  digitalinum  verum  is  dissolved  in 
sulphuric  acid  and  a  drop  of  very  dilute  nitric  acid,  iron  chloride 
solution,  or  bromine  is  added,  a  bluish-red  color  is  produced, 
similar  to  the  color  of  digitalis  flowers,  which  soon  disappears. 
The  touch  of  blue  in  the  red  coloration  has  always  been  con- 
sidered of  special  value. 
Keller 27  gives  the  following  reactions  for  the  digitalis  gluco- 
sides.  The  glucoside  is  dissolved  in  4  c.c.  of  glacial  acetic  acid, 
one  drop  of  a  dilute  solution  of  iron  chloride  is  added  and  the 
mixture  is  layered  on  to  4  c.c.  of  sulphuric  acid.  A  colored 
ring  appears  at  the  junction  of  the  liquids.  Digitonin  gives  a  pale 
pink  color,  which  soon  disappears.  Digitalinum  (verum)  gives 
rise  to  a  carmine  ring,  still  plainly  visible  as  a  permanent  violet- 
red  color  if  only  0.05  milligramme  of  digitalin  is  present  in  1  c.c. 
of  glacial  acetic  acid.  Digitalein  gives  a  similar  coloration,  but 
it  is  rather  fainter  and  not  so  constant.  Digitoxin  at  first  gives 
a  dirty  greenish-brown  color,  but  very  soon  the  uppermost  layer 
of  the  sulphuric  acid  is  seen  to  become  brownish-red,  while 
above  it  a  broad,  deep  bluish-green  band  is  formed,  the  color 
of  which  soon  passes  into  a  permanent  indigo-blue.  While  the 
mechanism  of  the  green  color  reaction  of  digitoxin  cannot  be 
Grandeau,  Comptes  rendus  de  1'academie  des  sciences  1864,  Vol.  58,  p.  1120. 
Buckingham,  American  Journal  of  Pharmacy  1873,  p.  149. 
Kiliani,  Archiv  der  Pharinazie,  Vol.  230,  p.  250. 
Keller,  Berichte  der  pharmazeutischen  Gesellschaft  Berlin  1895,  p.  275. 
